Questions from Homework 1—3

Homework #3:

  1. (9.85) (a) Write two resonance structures including formal charges for hydrazoic acid HN3.

(b) What are the bond orders of the N–N bonds?

(a)[ H – N- – N+ ≡ N ] ↔ [H – N ＝ N+＝ N- ]

  1. (9.67) Write resonance structures for (a) the nitrite ion, NO2-; (b) the nitrous oxide molecule, N2O.
  1. (9.64 c) Use formal charge to choose between different arrangement of atoms: (c) nitrosyl chloride, NOCl, ClNO, or NClO?
  1. Write possible resonance structures of: (a) NO2- (b) O3 (c) SO3
  1. Predict the hybrid orbital type of the central atoms of the following molecules and ions; and predict the shapes of electron pairs and the shapes of molecules: NO2, NF3, SO32-, CS2, BO33-, SiF4, H2S, ClO4-, ClO3-, SbCl5, ICl3, AlF63-, XeF4. (Please list your answers in a table.)

Homework #2:

  1. (8.45, e) Write the abbreviated electron configuration and orbital diagram for the ground state of each ion: (e) Ti4+

Solution: [Ar] (Common mistake: [Ar] 3d24s2)

  1. (8.47) Write the electron configuration for the first excited state of sodium ion.

Solution: 1s22s22p63s03p1(Common mistake: Na+, 1s22s22p6)

–Note: Compare the concept of “the first excited state” with “the first ionization energy”

  1. (8.62, d—e) Which one has higher value for IE1:

(d) B or Be;

(e) N or O?

Solution: (d) Be(e) N

–Note: IE1 does not always increases from left to right. Indeed, when there is a “full s-shell or half-full p-shell existing”, the IE1 is also higher than its adjacent neighbors.

  1. (8.84) Explain briefly why

(a)the IE1 of Al is less than the IE1 of Mg;

(b)the IE1 of S is less than the IE1 of P;

(c)although the IE1 of Na is lower than IE1 of Mg, but the IE2 of Na is higher than the IE2 of Mg;

(d)the IE1 of Ga is about the same as the IE1 of Al.

Homework #1:

  1. (3.49, b, e) What is the empirical formula of the following compounds:

(b)72.4% Fe and 27.6 O?

Solution: Fe3O4(Common mistake: FeO)

(e)93.71% C and 6.29% H?

Solution: C5H4(Common mistake: CH)

  1. (7.44) The wavelength of the yellow line in the emission spectrum of helium is 588 nm. What is the energy difference between the two energy levels involved in kJ/mol?

Solution: E = NA * h * c / λ(Common mistake: forget to multiply NA)

  1. (7.56, d) (d) What quantum numbers are possible for a 6d orbital?

Solution: n = 6; l = 2; ml = 0, ±1, ±2; ms = ±1/2