# Solutions 17

## S17.1

(a) eight electrons: ;

(b) eight electrons: ;

(c) no electrons

Be2+;

(d) eight electrons: ;

(e) no electrons

Ga3+;

(f) no electrons

Li+;

(g) eight electrons: ## S17.2

Write Lewis structures for the following:

a. H2 b. HBr c. PCl3 d. SF2 e. H2CCH2 f. HNNH g. H2CNH h. NO i. N2 j. CO k. CN ## S17.3

a When H and Cl are separate (the x axis) the energy is at a particular value. As they approach, it decreases to a minimum at 127 pm (the bond distance), and then it increases sharply as you get closer.

You can also find the potential energy function of H-Cl and take the derivative with respect to internuclear distance and find minimum.

1. $$H–Cl$$: $$energy of one bond=431 kJ/mol /N_A=431 \times 10^3 J/mol x \dfrac{1 mol}{6.02 \times 10^{23} bonds}=7.16 \times 10^{-19} J/bond$$

## S17.4

The single bond present in each molecule results from overlap of the relevant orbitals: F 2p orbitals in F2, the H 1s and F 2p orbitals in HF, and the Cl 3p orbital and Br 4p orbital in ClBr.

## S17.5

$$\ce{H–C≡N}$$ has two σ (H–C and C–N) and two π (making the CN triple bond). ## S17.6

An ionic bond wave function takes into account the probability that the electrons of a multiatomic molecule might exist on the same atom; the covalent bond wave function assumes they exist on separate atoms.