Problem Set 5.6: Bonding Review Complete the questions on your own sheet of paper.

1. Describe how the following pairs of atoms form bonds. Use diagrams and explanation to illustrate the important points. Write expected chemical formulas and name each chemical produced.

a) H atom(s) and F atom(s)

There is a mutual attraction of one atom’s electrons for another atom’s nucleus. This brings the atoms closer together so that they can share a pair of electrons. The shared pair of electrons is a covalent bond and the resulting compound is a molecule (a distinct unit and separate chemical species).

b) Na atom(s) and Cl atom(s)

There is a transfer of one (or more) electron from the metal to the nonmetal. This forms two ions (a cation and an anion). The ions are electrostatically attracted to each other. This is an ionic bond. The ions adopt a structure we call an ionic crystal lattice. The simplest ratio of ions in the lattice is referred to as a formula unit.

c) K atom(s) and P atom(s)

same as b) except use K instead of Na and P instead of Cl to make K⁺ [ P ]^3-

There is a transfer of one (or more) electron from the metal to the nonmetal. This forms two ions (a cation and an anion). The ions are electrostatically attracted to each other. This is an ionic bond. The ions adopt a structure we call an ionic crystal lattice. The simplest ratio of ions in the lattice is referred to as a formula unit.

d) P atom(s) and Br atom(s)

same as a) except use P instead of H and Br instead of F

There is a mutual attraction of one atom’s electrons for another atom’s nucleus. This brings the atoms closer together so that they can share a pair of electrons. The shared pair of electrons is a covalent bond and the resulting compound is a molecule (a distinct unit and separate chemical species).

e) Al atom(s) and F atom(s)

same as b) except use Al instead of Na and F instead of Cl to make Al³⁺ [ F ]^-

There is a transfer of one (or more) electron from the metal to the nonmetal. This forms two ions (a cation and an anion). The ions are electrostatically attracted to each other. This is an ionic bond. The ions adopt a structure we call an ionic crystal lattice. The simplest ratio of ions in the lattice is referred to as a formula unit.

2. Explain how a covalent bond is formed. (summarize text material pages 330 to 332 in your own words)

The electrons from one atom are attracted to the nucleus of another atom. The attraction is strong enough to overcome any electron-electron repulsion of between the two atoms. The atoms get close enough that they share a pair of electrons. This is a mutual attraction of each atom’s electrons to the others’ nucleus. This is done when both atoms are electron deficient and require more electrons in their valence shells.

3. Draw and describe an ionic crystal lattice. Draw a small piece of the crystal lattice structure.

An Ionic Crystal Lattice is a large network of alternating charged ions found in ionic compounds. See diagram. Ionic compounds exist in this way and cannot technically be called molecules. The empirical formula of ionic compound can be given by the simplest whole number ratio of the ions found in the compound.

4. Explain why covalently bonded materials are referred to as molecules, but ionic substances are referred to in terms of formula units. Begin by stating what these two ideas mean.

Molecules are distinct units made up of a specific number of atoms of each type of element found in the compound. It is applied only to covalently bonded materials. On the other hand, a formula unit is needed to express the formulas of ionic compounds since they exist as Ionic Crystal Lattices, where there is billions of each kind of ion connected within the lattice structure. A formula unit is the same as the empirical formula (simplest whole number ratio of ions) and is determined by working with the combining capacities (charges).

5. State the “Octet Rule”. Are there exceptions to this rule? Explain.

The “Octet Rule” states that all atoms want to become more stable by gaining a valence shell of 8 electrons. Exception to this rule would be H and He, which are satisfied by only 2 electrons. A better way of stating the rule: All atoms want a completely filled valence shell.

6. Draw Lewis (electron dot diagrams) and structural formulas (no electrons) of the following molecules:

a) Br2

b) HCl

c) N2

d) CH4

e) NI3

f) CH2ClF

g) CO2

h) PCl3 Skip this question

h) SO3^2-

j) HCN

k) NO Skip this question

l) C2H2

7. Draw Lewis Diagrams for the following atoms and indicate the number of bonding electrons, number of lone pairs, and expected number of covalent bonds each would make.

	a) Br	b) H	c) N	d) C	e) Ne	f) S
#l.p	3	0	1	0	4	2
# b.e.	1	1	3	4	0	2
# exp. bonds	1	1	3	4	0	2

8. What does the term isoelectronic mean?

Isoelectronic means “the same number of electrons”. You use this term in comparing two atoms or molecules.

9. State the shape of the following molecules.

a) C2H2	b) H2S	c) NI3	d) CH3F	e) C2F2I2	f) CH2ClF
linear	angular	trigonal pyramidal	tetrahedral	trigonal planar	tetrahedral
g) CO2	h) PCl3	i) PH4^+	j) HCN	k) NO	l) Br2
linear	linear	tetrahedral	linear	linear	linear

10. Draw all resonance structures of …. Skip this question