what needs to be done to convert a neutral nitrogen atom into an n3- species?

Chapter 7. Chemical Bonding and Molecular Geometry

7.3 Lewis Symbols and Structures

Learning Objectives

By the end of this section, yous volition be able to:

  • Write Lewis symbols for neutral atoms and ions
  • Draw Lewis structures depicting the bonding in unproblematic molecules

Thus far in this affiliate, nosotros have discussed the diverse types of bonds that form between atoms and/or ions. In all cases, these bonds involve the sharing or transfer of valence shell electrons betwixt atoms. In this department, we will explore the typical method for depicting valence beat out electrons and chemical bonds, namely Lewis symbols and Lewis structures.

Lewis Symbols

We use Lewis symbols to describe valence electron configurations of atoms and monatomic ions. A Lewis symbol consists of an elemental symbol surrounded past one dot for each of its valence electrons:

A Lewis structure of calcium is shown. A lone pair of electrons are shown to the right of the symbol.

Figure 1 shows the Lewis symbols for the elements of the tertiary period of the periodic table.

A table is shown that has three columns and nine rows. The header row reads
Figure one. Lewis symbols illustrating the number of valence electrons for each element in the third period of the periodic tabular array.

Lewis symbols tin as well be used to illustrate the formation of cations from atoms, as shown hither for sodium and calcium:

Two diagrams are shown. The left diagram shows a Lewis dot structure of sodium with one dot, then a right-facing arrow leading to a sodium symbol with a superscripted plus sign, a plus sign, and the letter

Likewise, they can be used to show the formation of anions from atoms, as shown hither for chlorine and sulfur:

Two diagrams are shown. The left diagram shows a Lewis dot structure of chlorine with seven dots and the letter

Figure 2 demonstrates the use of Lewis symbols to show the transfer of electrons during the germination of ionic compounds.

A table is shown with four rows. The header row reads
Figure 2. Cations are formed when atoms lose electrons, represented by fewer Lewis dots, whereas anions are formed past atoms gaining electrons. The total number of electrons does non change.

Lewis Structures

We also use Lewis symbols to indicate the formation of covalent bonds, which are shown in Lewis structures, drawings that depict the bonding in molecules and polyatomic ions. For example, when two chlorine atoms form a chlorine molecule, they share i pair of electrons:

A Lewis dot diagram shows a reaction. Two chlorine symbols, each surrounded by seven dots are separated by a plus sign. The dots on the first atom are all black and the dots on the second atom are all read. The phrase,

The Lewis structure indicates that each Cl atom has three pairs of electrons that are not used in bonding (called lone pairs) and one shared pair of electrons (written betwixt the atoms). A dash (or line) is sometimes used to betoken a shared pair of electrons:

Two Lewis structures are shown. The left-hand structure shows two H atoms connected by a single bond. The right-hand structure shows two C l atoms connected by a single bond and each surrounded by six dots.

A single shared pair of electrons is called a single bond. Each Cl cantlet interacts with eight valence electrons: the vi in the lonely pairs and the two in the single bail.

The Octet Rule

The other halogen molecules (F2, Brtwo, I2, and At2) course bonds similar those in the chlorine molecule: one single bond between atoms and iii lonely pairs of electrons per atom. This allows each halogen atom to take a noble gas electron configuration. The tendency of chief group atoms to course enough bonds to obtain eight valence electrons is known equally the octet rule.

The number of bonds that an atom tin form can often be predicted from the number of electrons needed to reach an octet (8 valence electrons); this is especially true of the nonmetals of the second period of the periodic table (C, N, O, and F). For example, each cantlet of a group fourteen element has four electrons in its outermost shell and therefore requires four more electrons to reach an octet. These iv electrons can be gained past forming 4 covalent bonds, as illustrated here for carbon in CCl4 (carbon tetrachloride) and silicon in SiHiv (silane). Because hydrogen only needs two electrons to fill its valence trounce, information technology is an exception to the octet rule. The transition elements and inner transition elements besides do not follow the octet rule:

Two sets of Lewis dot structures are shown. The left structures depict five C l symbols in a cross shape with eight dots around each, the word

Group 15 elements such equally nitrogen take five valence electrons in the diminutive Lewis symbol: one alone pair and three unpaired electrons. To obtain an octet, these atoms form three covalent bonds, as in NH3 (ammonia). Oxygen and other atoms in group sixteen obtain an octet by forming two covalent bonds:

Three Lewis structures labeled,

Double and Triple Bonds

As previously mentioned, when a pair of atoms shares ane pair of electrons, we phone call this a single bond. However, a pair of atoms may need to share more than one pair of electrons in order to accomplish the requisite octet. A double bond forms when two pairs of electrons are shared between a pair of atoms, equally between the carbon and oxygen atoms in CHiiO (formaldehyde) and between the two carbon atoms in CtwoHfour (ethylene):

Two pairs of Lewis structures are shown. The left pair of structures shows a carbon atom forming single bonds to two hydrogen atoms. There are four electrons between the C atom and an O atom. The O atom also has two pairs of dots. The word

A triple bond forms when three electron pairs are shared by a pair of atoms, as in carbon monoxide (CO) and the cyanide ion (CN):

Two pairs of Lewis structures are shown and connected by a right-facing arrow. The left pair of structures show a C atom and an O atom with six dots in between them and a lone pair on each. The word

Writing Lewis Structures with the Octet Rule

For very elementary molecules and molecular ions, nosotros can write the Lewis structures by merely pairing up the unpaired electrons on the constituent atoms. See these examples:

Three reactions are shown with Lewis dot diagrams. The first shows a hydrogen with one red dot, a plus sign and a bromine with seven dots, one of which is red, connected by a right-facing arrow to a hydrogen and bromine with a pair of red dots in between them. There are also three lone pairs on the bromine. The second reaction shows a hydrogen with a coefficient of two and one red dot, a plus sign, and a sulfur atom with six dots, two of which are red, connected by a right facing arrow to two hydrogen atoms and one sulfur atom. There are two red dots in between the two hydrogen atoms and the sulfur atom. Both pairs of these dots are red. The sulfur atom also has two lone pairs of dots. The third reaction shows two nitrogen atoms each with five dots, three of which are red, separated by a plus sign, and connected by a right-facing arrow to two nitrogen atoms with six red electron dots in between one another. Each nitrogen atom also has one lone pair of electrons.

For more complicated molecules and molecular ions, it is helpful to follow the step-past-step procedure outlined here:

  1. Determine the full number of valence (outer shell) electrons. For cations, subtract one electron for each positive charge. For anions, add one electron for each negative charge.
  2. Describe a skeleton construction of the molecule or ion, arranging the atoms effectually a fundamental atom. (Mostly, the least electronegative element should be placed in the heart.) Connect each atom to the central atom with a single bond (one electron pair).
  3. Distribute the remaining electrons as lonely pairs on the final atoms (except hydrogen), completing an octet effectually each atom.
  4. Place all remaining electrons on the central atom.
  5. Rearrange the electrons of the outer atoms to make multiple bonds with the central cantlet in club to obtain octets wherever possible.

Let us determine the Lewis structures of SiH4, CHO2−, NO+, and OF2 every bit examples in post-obit this procedure:

  1. Determine the full number of valence (outer crush) electrons in the molecule or ion.
    • For a molecule, we add together the number of valence electrons on each cantlet in the molecule:

      [latex]\begin{array}{r r l} \text{SiH}_4 & & \\[1em] & \text{Si: 4 valence electrons/atom} \times one \;\text{atom} & = four \\[1em] \rule[-0.5ex]{21em}{0.1ex}\hspace{-21em} + & \text{H: 1 valence electron/atom} \times 4 \;\text{atoms} & = 4 \\[1em] & & = 8 \;\text{valence electrons} \end{array}[/latex]

    • For a negative ion, such as CHO2 , we add the number of valence electrons on the atoms to the number of negative charges on the ion (one electron is gained for each single negative charge):

      [latex]\begin{array}{r r l} {\text{CHO}_2}^{-} & & \\[1em] & \text{C: 4 valence electrons/atom} \times ane \;\text{atom} & = 4 \\[1em] & \text{H: ane valence electron/atom} \times 1 \;\text{atom} & = 1 \\[1em] & \text{O: half-dozen valence electrons/atom} \times 2 \;\text{atoms} & = 12 \\[1em] \dominion[-0.5ex]{21.5em}{0.1ex}\hspace{-21.5em} + & 1\;\text{additional electron} & = 1 \\[1em] & & = eighteen \;\text{valence electrons} \stop{array}[/latex]

    • For a positive ion, such as NO+, we add the number of valence electrons on the atoms in the ion and then subtract the number of positive charges on the ion (one electron is lost for each unmarried positive charge) from the full number of valence electrons:

      [latex]\brainstorm{assortment}{r r l} \text{NO}^{+} & & \\[1em] & \text{N: 5 valence electrons/cantlet} \times ane \;\text{cantlet} & = 5 \\[1em] & \text{O: 6 valence electrons/atom} \times 1 \;\text{atom} & = 6 \\[1em] \dominion[-0.5ex]{21em}{0.1ex}\hspace{-21em} + & -1 \;\text{electron (positive charge)} & = -1 \\[1em] & & = x \;\text{valence electrons} \end{array}[/latex]

    • Since OFii is a neutral molecule, we only add the number of valence electrons:

      [latex]\begin{array}{r r fifty} \text{OF}_{2} & & \\[1em] & \text{O: 6 valence electrons/atom} \times ane \;\text{atom} & = 6 \\[1em] \rule[-0.5ex]{21em}{0.1ex}\hspace{-21em} + & \text{F: seven valence electrons/atom} \times two \;\text{atoms} & = 14 \\[1em] & & = 20 \;\text{valence electrons} \cease{array}[/latex]

  2. Draw a skeleton structure of the molecule or ion, arranging the atoms around a key atom and connecting each atom to the primal atom with a single (one electron pair) bond. (Note that nosotros denote ions with brackets around the structure, indicating the charge outside the brackets:)Four Lewis diagrams are shown. The first shows one silicon single boned to four hydrogen atoms. The second shows a carbon which forms a single bond with an oxygen and a hydrogen and a double bond with a second oxygen. This structure is surrounded by brackets and has a superscripted negative sign near the upper right corner. The third structure shows a nitrogen single bonded to an oxygen and surrounded by brackets with a superscripted plus sign in the upper right corner. The last structure shows two fluorine atoms single bonded to a central oxygen.When several arrangements of atoms are possible, equally for CHOii , we must use experimental evidence to choose the correct i. In full general, the less electronegative elements are more probable to exist central atoms. In CHOtwo , the less electronegative carbon atom occupies the fundamental position with the oxygen and hydrogen atoms surrounding information technology. Other examples include P in POCl3, Due south in And soii, and Cl in ClOiv . An exception is that hydrogen is almost never a primal cantlet. As the most electronegative chemical element, fluorine also cannot be a cardinal atom.
  3. Distribute the remaining electrons as lone pairs on the terminal atoms (except hydrogen) to complete their valence shells with an octet of electrons.
    • In that location are no remaining electrons on SiH4, so it is unchanged:Four Lewis structures are shown. The first shows one silicon single boned to four hydrogen atoms. The second shows a carbon single bonded to two oxygen atoms that each have three lone pairs and single bonded to a hydrogen. This structure is surrounded by brackets and has a superscripted negative sign near the upper right corner. The third structure shows a nitrogen single bonded to an oxygen, each with three lone pairs of electrons. This structure is surrounded by brackets with a superscripted plus sign in the upper right corner. The last structure shows two fluorine atoms, each with three lone pairs of electrons, single bonded to a central oxygen.
  4. Identify all remaining electrons on the fundamental atom.
    • For SiHiv, CHO2 , and NO+, there are no remaining electrons; we already placed all of the electrons determined in Step i.
    • For OF2, nosotros had 16 electrons remaining in Step 3, and we placed 12, leaving iv to be placed on the cardinal atom:A Lewis structure shows two fluorine atoms, each with three lone pairs of electrons, single bonded to a central oxygen which has two lone pairs of electrons.
  5. Rearrange the electrons of the outer atoms to make multiple bonds with the central atom in order to obtain octets wherever possible.

Example ane

Writing Lewis Structures
NASA's Cassini-Huygens mission detected a big cloud of toxic hydrogen cyanide (HCN) on Titan, one of Saturn's moons. Titan also contains ethane (HthreeCCH3), acetylene (HCCH), and ammonia (NHiii). What are the Lewis structures of these molecules?

Solution

  1. Summate the number of valence electrons.HCN: (ane × one) + (iv × 1) + (5 × 1) = 10H3CCH3: (1 × 3) + (2 × four) + (1 × 3) = 14HCCH: (1 × 1) + (2 × 4) + (1 × ane) = 10NH3: (five × 1) + (3 × i) = 8
  2. Depict a skeleton and connect the atoms with single bonds. Retrieve that H is never a central cantlet:Four Lewis structures are shown. The first structure shows a carbon atom single bonded to a hydrogen atom and a nitrogen atom. The second structure shows two carbon atoms single bonded to one another. Each is single bonded to three hydrogen atoms. The third structure shows two carbon atoms single bonded to one another and each single bonded to one hydrogen atom. The fourth structure shows a nitrogen atom single bonded to three hydrogen atoms.
  3. Where needed, distribute electrons to the final atoms: Four Lewis structures are shown. The first structure shows a carbon atom single bonded to a hydrogen atom and a nitrogen atom, which has three lone pairs of electrons. The second structure shows two carbon atoms single bonded to one another. Each is single bonded to three hydrogen atoms. The third structure shows two carbon atoms single bonded to one another and each single bonded to one hydrogen atom. The fourth structure shows a nitrogen atom single bonded to three hydrogen atoms.HCN: 6 electrons placed on NH3CCH3: no electrons remainHCCH: no final atoms capable of accepting electrons

    NHthree: no final atoms capable of accepting electrons

  4. Where needed, place remaining electrons on the central cantlet: Four Lewis structures are shown. The first structure shows a carbon atom single bonded to a hydrogen atom and a nitrogen atom, which has three lone pairs of electrons. The second structure shows two carbon atoms single bonded to one another. Each is single bonded to three hydrogen atoms. The third structure shows two carbon atoms, each with a lone pair of electrons, single bonded to one another and each single bonded to one hydrogen atom. The fourth structure shows a nitrogen atom with a lone pair of electrons single bonded to three hydrogen atoms.HCN: no electrons remainHthreeCCH3: no electrons remainHCCH: four electrons placed on carbon

    NHiii: two electrons placed on nitrogen

  5. Where needed, rearrange electrons to form multiple bonds in order to obtain an octet on each atom:HCN: grade 2 more C–N bondsHthreeCCH3: all atoms have the right number of electronsHCCH: form a triple bond between the two carbon atomsNHthree: all atoms have the right number of electrons

    Four Lewis structures are shown. The first structure shows a carbon atom single bonded to a hydrogen atom and a nitrogen atom, which has three lone pairs of electrons. Two curved arrows point from the nitrogen to the carbon. Below this structure is the word

Check Your Learning
Both carbon monoxide, CO, and carbon dioxide, CO2, are products of the combustion of fossil fuels. Both of these gases also cause issues: CO is toxic and COii has been implicated in global climate alter. What are the Lewis structures of these ii molecules?

Respond:

Two Lewis structures are shown. The left shows a carbon triple bonded to an oxygen, each with a lone electron pair. The right structure shows a carbon double bonded to an oxygen on each side. Each oxygen has two lone pairs of electrons.

Fullerene Chemistry

Carbon soot has been known to human since prehistoric times, only information technology was not until fairly recently that the molecular structure of the primary component of soot was discovered. In 1996, the Nobel Prize in Chemistry was awarded to Richard Smalley (Figure 3), Robert Curl, and Harold Kroto for their work in discovering a new form of carbon, the C60 buckminsterfullerene molecule (Figure ane in Chapter 7 Introduction). An unabridged form of compounds, including spheres and tubes of diverse shapes, were discovered based on Cthreescore. This type of molecule, called a fullerene, shows hope in a multifariousness of applications. Considering of their size and shape, fullerenes can encapsulate other molecules, so they take shown potential in various applications from hydrogen storage to targeted drug commitment systems. They also possess unique electronic and optical properties that have been put to good employ in solar powered devices and chemical sensors.

A photo of Richard Smalley is shown.
Figure 3. Richard Smalley (1943–2005), a professor of physics, chemistry, and astronomy at Rice Academy, was one of the leading advocates for fullerene chemistry. Upon his death in 2005, the US Senate honored him as the "Begetter of Nanotechnology." (credit: United States Department of Energy)

Exceptions to the Octet Dominion

Many covalent molecules have central atoms that do not have eight electrons in their Lewis structures. These molecules autumn into three categories:

  • Odd-electron molecules have an odd number of valence electrons, and therefore have an unpaired electron.
  • Electron-scarce molecules have a key atom that has fewer electrons than needed for a noble gas configuration.
  • Hypervalent molecules have a central atom that has more electrons than needed for a element of group 0 configuration.

Odd-electron Molecules

We call molecules that contain an odd number of electrons free radicals. Nitric oxide, NO, is an instance of an odd-electron molecule; it is produced in internal combustion engines when oxygen and nitrogen react at high temperatures.

To describe the Lewis structure for an odd-electron molecule similar NO, nosotros follow the same five steps we would for other molecules, simply with a few pocket-size changes:

  1. Decide the total number of valence (outer trounce) electrons. The sum of the valence electrons is 5 (from N) + 6 (from O) = eleven. The odd number immediately tells us that we have a free radical, so we know that non every atom tin have eight electrons in its valence beat.
  2. Describe a skeleton construction of the molecule. We tin easily draw a skeleton with an North–O unmarried bond:N–O
  3. Distribute the remaining electrons as lone pairs on the final atoms. In this case, at that place is no central atom, so nosotros distribute the electrons around both atoms. We give eight electrons to the more electronegative atom in these situations; thus oxygen has the filled valence shell:
    A Lewis structure shows a nitrogen atom, with one lone pair and one lone electron single bonded to an oxygen atom with three lone pairs of electrons.
  4. Place all remaining electrons on the cardinal atom. Since there are no remaining electrons, this footstep does not use.
  5. Rearrange the electrons to brand multiple bonds with the central atom in order to obtain octets wherever possible. We know that an odd-electron molecule cannot take an octet for every cantlet, simply we desire to get each atom as close to an octet as possible. In this case, nitrogen has only five electrons around information technology. To motility closer to an octet for nitrogen, we have one of the lone pairs from oxygen and utilize it to form a NO double bail. (Nosotros cannot take another lone pair of electrons on oxygen and form a triple bond because nitrogen would then take 9 electrons:)
    A Lewis structure shows a nitrogen atom, with one lone pair and one lone electron double bonded to an oxygen atom with two lone pairs of electrons.

Electron-scarce Molecules

We will as well come across a few molecules that incorporate key atoms that do non have a filled valence beat. Generally, these are molecules with key atoms from groups two and 12, outer atoms that are hydrogen, or other atoms that practice not course multiple bonds. For instance, in the Lewis structures of beryllium dihydride, BeHtwo, and boron trifluoride, BF3, the beryllium and boron atoms each have only four and six electrons, respectively. It is possible to depict a construction with a double bond between a boron atom and a fluorine atom in BF3, satisfying the octet rule, simply experimental evidence indicates the bond lengths are closer to that expected for B–F single bonds. This suggests the best Lewis structure has three B–F unmarried bonds and an electron deficient boron. The reactivity of the compound is also consequent with an electron deficient boron. Still, the B–F bonds are slightly shorter than what is really expected for B–F single bonds, indicating that some double bond character is found in the bodily molecule.

Two Lewis structures are shown. The left shows a beryllium atom single bonded to two hydrogen atoms. The right shows a boron atom single bonded to three fluorine atoms, each with three lone pairs of electrons.

An atom like the boron atom in BFiii, which does not have 8 electrons, is very reactive. It readily combines with a molecule containing an atom with a lonely pair of electrons. For example, NH3 reacts with BF3 because the solitary pair on nitrogen can exist shared with the boron cantlet:

A reaction is shown with three Lewis diagrams. The left diagram shows a boron atom single bonded to three fluorine atoms, each with three lone pairs of electrons. There is a plus sign. The next structure shows a nitrogen atom with one lone pair of electrons single bonded to three hydrogen atoms. A right-facing arrow leads to the final Lewis structure that shows a boron atom single bonded to a nitrogen atom and single bonded to three fluorine atoms, each with three lone pairs of electrons. The nitrogen atom is also single bonded to three hydrogen atoms. The bond between the boron atom and the nitrogen atom is colored red.

Hypervalent Molecules

Elements in the second period of the periodic tabular array (north = two) tin can adapt only viii electrons in their valence shell orbitals because they accept but four valence orbitals (one 2s and three 2p orbitals). Elements in the tertiary and higher periods (n ≥ three) accept more than four valence orbitals and can share more than four pairs of electrons with other atoms because they have empty d orbitals in the same crush. Molecules formed from these elements are sometimes called hypervalent molecules. Figure four shows the Lewis structures for two hypervalent molecules, PClv and SFhalf-dozen.

Two Lewis structures are shown. The left shows a phosphorus atom single bonded to five chlorine atoms, each with three lone pairs of electrons. The right shows a sulfur atom single bonded to six fluorine atoms, each with three lone pairs of electrons.
Figure 4. In PCl5, the key cantlet phosphorus shares v pairs of electrons. In SF6, sulfur shares six pairs of electrons.

In some hypervalent molecules, such as IF5 and XeF4, some of the electrons in the outer shell of the central atom are lone pairs:

Two Lewis structures are shown. The left shows an iodine atom with one lone pair single bonded to five fluorine atoms, each with three lone pairs of electrons. The right diagram shows a xenon atom with two lone pairs of electrons single bonded to four fluorine atoms, each with three lone pairs of electrons.

When we write the Lewis structures for these molecules, we find that we have electrons left over after filling the valence shells of the outer atoms with eight electrons. These additional electrons must exist assigned to the central atom.

Instance two

Writing Lewis Structures: Octet Dominion Violations
Xenon is a noble gas, but it forms a number of stable compounds. We examined XeFfour earlier. What are the Lewis structures of XeFii and XeF6?

Solution
We can describe the Lewis structure of any covalent molecule by post-obit the six steps discussed earlier. In this example, nosotros tin condense the last few steps, since not all of them apply.

  1. Calculate the number of valence electrons: XeF2: viii + (ii × 7) = 22XeF6: 8 + (6 × 7) = 50
  2. Draw a skeleton joining the atoms by single bonds. Xenon will exist the primal cantlet considering fluorine cannot exist a central cantlet:
    Two Lewis diagrams are shown. The left depicts a xenon atom single bonded to two fluorine atoms. The right shows a xenon atom single bonded to six fluorine atoms.
  3. Distribute the remaining electrons.XeFii: We place three lonely pairs of electrons around each F atom, accounting for 12 electrons and giving each F cantlet 8 electrons. Thus, vi electrons (three lone pairs) remain. These lone pairs must be placed on the Xe cantlet. This is acceptable because Xe atoms accept empty valence shell d orbitals and tin accommodate more than eight electrons. The Lewis structure of XeF2 shows 2 bonding pairs and three alone pairs of electrons around the Xe atom:
    A Lewis diagram shows a xenon atom with three lone pairs of electrons single bonded to two fluorine atoms, each with three lone pairs of electrons.XeF6: We place three lone pairs of electrons around each F cantlet, bookkeeping for 36 electrons. 2 electrons remain, and this lone pair is placed on the Xe atom:This structure shows a xenon atom single bonded to six fluorine atoms. Each fluorine atom has three lone pairs of electrons.

Cheque Your Learning
The halogens form a class of compounds chosen the interhalogens, in which halogen atoms covalently bond to each other. Write the Lewis structures for the interhalogens BrCl3 and ICl4 .

Answer:

Two Lewis structures are shown. The left depicts a bromine atom with two lone pairs of electrons single bonded to three chlorine atoms, each with three lone pairs of electrons. The right shows an iodine atom, with two lone pairs of electrons, single boned to four chlorine atoms, each with three lone pairs of electrons. This structure is surrounded by brackets and has a superscripted negative sign.

Primal Concepts and Summary

Valence electronic structures can exist visualized by cartoon Lewis symbols (for atoms and monatomic ions) and Lewis structures (for molecules and polyatomic ions). Alone pairs, unpaired electrons, and single, double, or triple bonds are used to indicate where the valence electrons are located around each atom in a Lewis structure. Most structures—especially those containing second row elements—obey the octet rule, in which every atom (except H) is surrounded past eight electrons. Exceptions to the octet dominion occur for odd-electron molecules (gratuitous radicals), electron-scarce molecules, and hypervalent molecules.

Chemistry End of Chapter Exercises

  1. Write the Lewis symbols for each of the following ions:

    (a) Asthree–

    (b) I

    (c) Be2+

    (d) O2–

    (eastward) Gathree+

    (f) Li+

    (1000) N3–

  2. Many monatomic ions are establish in seawater, including the ions formed from the following list of elements. Write the Lewis symbols for the monatomic ions formed from the following elements:

    (a) Cl

    (b) Na

    (c) Mg

    (d) Ca

    (e) K

    (f) Br

    (g) Sr

    (h) F

  3. Write the Lewis symbols of the ions in each of the following ionic compounds and the Lewis symbols of the atom from which they are formed:

    (a) MgS

    (b) Al2Oiii

    (c) GaCl3

    (d) K2O

    (e) Li3N

    (f) KF

  4. In the Lewis structures listed here, Grand and Ten represent various elements in the third period of the periodic table. Write the formula of each chemical compound using the chemical symbols of each element:

    (a)

    Two Lewis structures are shown side-by-side, each surrounded by brackets. The left structure shows the symbol M with a superscripted two positive sign. The right shows the symbol X surrounded by four lone pairs of electrons with a superscripted two negative sign outside of the brackets.

    (b)

    Two Lewis structures are shown side-by-side, each surrounded by brackets. The left structure shows the symbol M with a superscripted three positive sign. The right structure shows the symbol X surrounded by four lone pairs of electrons with a superscripted negative sign and a subscripted three both outside of the brackets.

    (c)

    Two Lewis structures are shown side-by-side, each surrounded by brackets. The left structure shows the symbol M with a superscripted positive sign and a subscripted two outside of the brackets. The right structure shows the symbol X surrounded by four lone pairs of electrons with a superscripted two negative sign outside of the brackets.

    (d)

    Two Lewis structures are shown side-by-side, each surrounded by brackets. The left structure shows the symbol M with a superscripted three positive sign and a subscripted two outside of the brackets. The right structure shows the symbol X surrounded by four lone pairs of electrons with a superscripted two negative sign and subscripted three both outside of the brackets.

  5. Write the Lewis construction for the diatomic molecule Ptwo, an unstable form of phosphorus found in loftier-temperature phosphorus vapor.
  6. Write Lewis structures for the following:

    (a) Hii

    (b) HBr

    (c) PClthree

    (d) SFii

    (due east) HiiCCH2

    (f) HNNH

    (g) HtwoCNH

    (h) NO

    (i) N2

    (j) CO

    (one thousand) CN

  7. Write Lewis structures for the following:

    (a) O2

    (b) HtwoCO

    (c) AsFthree

    (d) ClNO

    (e) SiCl4

    (f) H3O+

    (thousand) NH4 +

    (h) BF4

    (i) HCCH

    (j) ClCN

    (k) C2 2+

  8. Write Lewis structures for the following:

    (a) ClF3

    (b) PCl5

    (c) BF3

    (d) PFhalf dozen

  9. Write Lewis structures for the following:

    (a) SeFsix

    (b) XeF4

    (c) SeCl3 +

    (d) CltwoBBClii (contains a B–B bond)

  10. Write Lewis structures for:

    (a) PO4 3−

    (b) ICl4

    (c) Then3 2−

    (d) HONO

  11. Correct the post-obit statement: "The bonds in solid PbCl2 are ionic; the bond in a HCl molecule is covalent. Thus, all of the valence electrons in PbClii are located on the Cl ions, and all of the valence electrons in a HCl molecule are shared between the H and Cl atoms."
  12. Write Lewis structures for the post-obit molecules or ions:

    (a) SbHthree

    (b) XeFtwo

    (c) Se8 (a cyclic molecule with a ring of 8 Se atoms)

  13. Methanol, H3COH, is used equally the fuel in some race cars. Ethanol, CtwoH5OH, is used extensively as motor fuel in Brazil. Both methanol and ethanol produce CO2 and H2O when they burn. Write the chemic equations for these combustion reactions using Lewis structures instead of chemical formulas.
  14. Many planets in our solar organization comprise organic chemicals including methane (CHfour) and traces of ethylene (CtwoH4), ethane (C2H6), propyne (HiiiCCCH), and diacetylene (HCCCCH). Write the Lewis structures for each of these molecules.
  15. Carbon tetrachloride was formerly used in fire extinguishers for electric fires. It is no longer used for this purpose because of the formation of the toxic gas phosgene, CliiCO. Write the Lewis structures for carbon tetrachloride and phosgene.
  16. Identify the atoms that represent to each of the following electron configurations. Then, write the Lewis symbol for the common ion formed from each atom:

    (a) 1south 22s ii2p 5

    (b) isouth 22s 22p 6threedue south 2

    (c) 1s 22southward iitwop half dozen3due south 23p half dozen4due south twothreed 10

    (d) 1s twotwosouth two2p 6threes iithreep half dozen4s 23d ten4p 4

    (due east) 1s 22s 22p 63southward two3p 64s ii3d 104p ane

  17. The organization of atoms in several biologically of import molecules is given here. Complete the Lewis structures of these molecules by adding multiple bonds and lone pairs. Do not add any more atoms.

    (a) the amino acrid serine:

    A Lewis structure is shown. A nitrogen atom is single bonded to two hydrogen atoms and a carbon atom. The carbon atom is single bonded to a hydrogen atom and two other carbon atoms. One of these carbon atoms is single bonded to two hydrogen atoms and an oxygen atom. The oxygen atom is bonded to a hydrogen atom. The other carbon atom is single bonded to two oxygen atoms, one of which is bonded to a hydrogen atom.

    (b) urea:

    A Lewis structure is shown. A nitrogen atom is single bonded to two hydrogen atoms and a carbon atom. The carbon atom is single bonded to an oxygen atom and another nitrogen atom. That nitrogen atom is then single bonded to two hydrogen atoms.

    (c) pyruvic acrid:

    A Lewis structure is shown. A carbon atom is single bonded to three hydrogen atoms and another carbon atom. The second carbon atom is single bonded to an oxygen atom and a third carbon atom. This carbon is then single bonded to two oxygen atoms, one of which is single bonded to a hydrogen atom.

    (d) uracil:

    A Lewis hexagonal ring structure is shown. From the top of the ring (moving clockwise), three carbon atoms, one nitrogen atom, a carbon atom, and a nitrogen atom are single bonded to each another. The top carbon atom is single bonded to an oxygen atom. The second and third carbons and the nitrogen atom are each single bonded to a hydrogen atom. The next carbon atom is single bonded to an oxygen atom, and the last nitrogen atom is single bonded to a hydrogen atom.

    (due east) carbonic acid:

    A Lewis structure is shown. A carbon atom is single bonded to three oxygen atoms. Two of those oxygen atoms are each single bonded to a hydrogen atom.

  18. A compound with a molar mass of about 28 g/mol contains 85.7% carbon and 14.3% hydrogen by mass. Write the Lewis structure for a molecule of the compound.
  19. A compound with a molar mass of well-nigh 42 thou/mol contains 85.7% carbon and 14.three% hydrogen past mass. Write the Lewis structure for a molecule of the compound.
  20. Two arrangements of atoms are possible for a compound with a molar mass of about 45 g/mol that contains 52.ii% C, 13.1% H, and 34.vii% O by mass. Write the Lewis structures for the two molecules.
  21. How are single, double, and triple bonds similar? How exercise they differ?

Glossary

double bail
covalent bail in which two pairs of electrons are shared between 2 atoms
free radical
molecule that contains an odd number of electrons
hypervalent molecule
molecule containing at least i master group element that has more than than eight electrons in its valence beat
Lewis structure
diagram showing lone pairs and bonding pairs of electrons in a molecule or an ion
Lewis symbol
symbol for an element or monatomic ion that uses a dot to stand for each valence electron in the chemical element or ion
lonely pair
two (a pair of) valence electrons that are not used to course a covalent bond
octet rule
guideline that states master group atoms will grade structures in which eight valence electrons interact with each nucleus, counting bonding electrons as interacting with both atoms connected past the bond
unmarried bond
bond in which a unmarried pair of electrons is shared betwixt two atoms
triple bond
bond in which three pairs of electrons are shared between 2 atoms

Solutions

Answers to Chemistry End of Affiliate Exercises

one. (a) eight electrons:
A Lewis dot diagram shows the symbol for arsenic, A s, surrounded by eight dots and a superscripted three negative sign.;

(b) eight electrons:

A Lewis dot diagram shows the symbol for iodine, I, surrounded by eight dots and a superscripted negative sign.;

(c) no electrons

Exist2+;

(d) eight electrons:

A Lewis dot diagram shows the symbol for oxygen, O, surrounded by eight dots and a superscripted two negative sign.;

(e) no electrons

Gathree+;

(f) no electrons

Li+;

(g) 8 electrons:

A Lewis dot diagram shows the symbol for nitrogen, N, surrounded by eight dots and a superscripted three negative sign.

3. (a)

Two Lewis structures are shown. The left shows the symbol M g with a superscripted two positive sign while the right shows the symbol S surrounded by eight dots and a superscripted two negative sign.;

(b)

Two Lewis structures are shown. The left shows the symbol A l with a superscripted three positive sign while the right shows the symbol O surrounded by eight dots and a superscripted two negative sign.;

(c)

Two Lewis structures are shown. The left shows the symbol G a with a superscripted three positive sign while the right shows the symbol C l surrounded by eight dots and a superscripted negative sign.;

(d)

Two Lewis structures are shown. The left shows the symbol K with a superscripted positive sign while the right shows the symbol O surrounded by eight dots and a superscripted two negative sign.>;

(e)

Two Lewis structures are shown. The left shows the symbol L i with a superscripted positive sign while the right shows the symbol N surrounded by eight dots and a superscripted three negative sign.;

(f)

Two Lewis structures are shown. The left shows the symbol K with a superscripted positive sign while the right shows the symbol F surrounded by eight dots and a superscripted negative sign.

5.
A Lewis diagram shows two phosphorus atoms triple bonded together each with one lone electron pair.

7. (a)
A Lewis structure shows two oxygen atoms double bonded together, and each has two lone pairs of electrons.

In this case, the Lewis structure is inadequate to describe the fact that experimental studies have shown two unpaired electrons in each oxygen molecule.

(b)

A Lewis structure shows a carbon atom that is single bonded to two hydrogen atoms and double bonded to an oxygen atom. The oxygen atom has two lone pairs of electrons.;

(c)

A Lewis structure shows an arsenic atom single bonded to three fluorine atoms. Each fluorine atom has a lone pair of electrons.;

(d)

A Lewis structure shows a nitrogen atom with a lone pair of electrons single bonded to a chlorine atom that has three lone pairs of electrons. The nitrogen is also double bonded to an oxygen which has two lone pairs of electrons. ;

(due east)

A Lewis structure shows a silicon atom that is single bonded to four chlorine atoms. Each chlorine atom has three lone pairs of electrons.;

(f)

A Lewis structure shows an oxygen atom with a lone pair of electrons single bonded to three hydrogen atoms. The structure is surrounded by brackets with a superscripted positive sign.;

(g)

A Lewis structure shows a nitrogen atom single bonded to four hydrogen atoms. The structure is surrounded by brackets with a superscripted positive sign.;

(h)

A Lewis structure shows a boron atom single bonded to four fluorine atoms. Each fluorine atom has three lone pairs of electrons. The structure is surrounded by brackets with a superscripted negative sign.;

(i)

A Lewis structure shows two carbon atoms that are triple bonded together. Each carbon is also single bonded to a hydrogen atom.;

(j)

A Lewis structure shows a carbon atom that is triple bonded to a nitrogen atom that has one lone pair of electrons. The carbon is also single bonded to a chlorine atom that has three lone pairs of electrons.;

(yard)

A Lewis structure shows two carbon atoms joined with a triple bond. A superscripted 2 positive sign lies to the right of the second carbon.

9. (a) SeF6:
A Lewis structure shows a selenium atom single bonded to six fluorine atoms, each with three lone pairs of electrons.;

(b) XeFfour:

A Lewis structure shows a xenon atom with two lone pairs of electrons. It is single bonded to four fluorine atoms each with three lone pairs of electrons.;

(c) SeCliii +:

A Lewis structure shows a selenium atom with one lone pair of electrons single bonded to three chlorine atoms each with three lone pairs of electrons. The whole structure is surrounded by brackets.;

(d) CltwoBBCl2:

A Lewis structure shows two boron atoms that are single bonded together. Each is also single bonded to two chlorine atoms that both have three lone pairs of electrons.

11. Ii valence electrons per Pb atom are transferred to Cl atoms; the resulting Leadii+ ion has a 6s 2 valence trounce configuration. Two of the valence electrons in the HCl molecule are shared, and the other six are located on the Cl cantlet as lone pairs of electrons.

13.
Two reactions are shown using Lewis structures. The top reaction shows a carbon atom, single bonded to three hydrogen atoms and single bonded to an oxygen atom with two lone pairs of electrons. The oxygen atom is also bonded to a hydrogen atom. This is followed by a plus sign and the number one point five, followed by two oxygen atoms bonded together with a double bond and each with two lone pairs of electrons. A right-facing arrow leads to a carbon atom that is double bonded to two oxygen atoms, each of which has two lone pairs of electrons. This structure is followed by a plus sign, a number two, and a structure made up of an oxygen with two lone pairs of electrons single bonded to two hydrogen atoms. The bottom reaction shows a carbon atom, single bonded to three hydrogen atoms and single bonded to another carbon atom. The second carbon atom is single bonded to two hydrogen atoms and one oxygen atom with two lone pairs of electrons. The oxygen atom is also bonded to a hydrogen atom. This is followed by a plus sign and the number three, followed by two oxygen atoms bonded together with a double bond. Each oxygen atom has two lone pairs of electrons. A right-facing arrow leads to a number two and a carbon atom that is double bonded to two oxygen atoms, each of which has two lone pairs of electrons. This structure is followed by a plus sign, a number three, and a structure made up of an oxygen with two lone pairs of electrons single bonded to two hydrogen atoms.

15.
Two Lewis structures are shown. The left depicts a carbon atom single bonded to four chlorine atoms, each with three lone pairs of electrons. The right shows a carbon atom double bonded to an oxygen atom that has two lone pairs of electrons. The carbon atom is also single bonded to two chlorine atoms, each of which has three lone pairs of electrons.

17. (a)
A Lewis structure is shown. A nitrogen atom is single bonded to two hydrogen atoms and a carbon atom. The carbon atom is single bonded to a hydrogen atom and two other carbon atoms. One of these carbon atoms is single bonded to two hydrogen atoms and an oxygen atom. The oxygen atom is bonded to a hydrogen atom. The other carbon is single bonded to two oxygen atoms, one of which is bonded to a hydrogen atom. The oxygen atoms have two lone pairs of electron dots, and the nitrogen atom has one lone pair of electron dots.;

(b)

A Lewis structure is shown. A nitrogen atom is single bonded to two hydrogen atoms and a carbon atom. The carbon atom is single bonded to an oxygen atom and one nitrogen atom. That nitrogen atom is then single bonded to two hydrogen atoms. The oxygen atom has two lone pairs of electron dots, and the nitrogen atoms have one lone pair of electron dots each.;

(c)

A Lewis structure is shown. A carbon atom is single bonded to three hydrogen atoms and a carbon atom. The carbon atom is single bonded to an oxygen atom and a third carbon atom. This carbon is then single bonded to two oxygen atoms, one of which is single bonded to a hydrogen atom. Each oxygen atom has two lone pairs of electron dots.;

(d)

A Lewis hexagonal ring structure is shown. From the top of the ring, three carbon atoms, one nitrogen atom, a carbon atom and a nitrogen atom are single bonded to one another. The top carbon is single bonded to an oxygen, the second and third carbons and the nitrogen atom are each single bonded to a hydrogen atom. The next carbon is single bonded to an oxygen atom and the last nitrogen is single bonded to a hydrogen atom. The oxygen atoms have two lone pairs of electron dots, and the nitrogen atoms have one lone pair of electron dots.;

(e)

A Lewis structure is shown. A carbon atom is single bonded to three oxygen atoms. Two of those oxygen atoms are each single bonded to a hydrogen atom. Each oxygen atom has two lone pairs of electron dots.

19.
A Lewis structure is shown. A carbon atom is single bonded to three hydrogen atoms and another carbon atom. The second carbon atom is double bonded to another carbon atom and single bonded to a hydrogen atom. The last carbon is single bonded to two hydrogen atoms.

21. Each bond includes a sharing of electrons betwixt atoms. 2 electrons are shared in a unmarried bond; four electrons are shared in a double bond; and half dozen electrons are shared in a triple bail.

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Source: https://opentextbc.ca/chemistry/chapter/7-3-lewis-symbols-and-structures/

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