Chem 341 Inorganic Chemistry

Midterm Exam #1, Fall 2000

NAME: _________________________________

No aids are allowed for this exam. Periodic tables are provided on the last page (feel free to separate from your exam and keep in front of you).

Clear, informative answers will score the highest marks on this exam. Partial marks will be rewarded where applicable, so be sure to make your best attempt at all questions.

There are four questions, each worth 15 marks, for a maximum possible score of 60. For a given question, each part is worth an equal number of marks.

Duration: 60 minutes.

1. Draw the Lewis Dot diagrams for the following molecules, indicating formal charges and reasonable resonance structures, where applicable. Based on VSEPR rules, what is the molecular geometry for each (with respect to the central atom)?

(a) HNO3

(b) H3B(CO)

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(c) linear I3-

(d) IF4+

(e) IF4-

2. Consider the atom Ti (Z = 22).

(a) Give the ground state electronic configurations for Ti, Ti+ and Ti4+.

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(b) For Ti+ only, give the quantum number n, l, ml and s for each valence electron (note: ml can be any reasonable value).

(c) For Ti only, draw the orbitals in which the valence electrons reside, using spherical coordinates to indicate any angular nodes (note: if the electrons reside in degenerate orbitals, you can choose your favourite orbitals). Also give the number of radial nodes and sketch the radial distribution function for each orbital.

(d) Compare Ti with its neighbours in the first row of transition metals, Sc and V, in terms of r, IE, EA and en and explain the trend.

(e) Of Ti+, Ti3+ and Ti4+, which do you think is the most commonly occurring cation, and for what reason(s)?

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3. For each of the following planar molecules, list as many symmetry elements as you can (note: the phenyl ring is resonance-stabilized, and all C-C bonds are of equal length). You do not have to actually draw the symmetry elements, but list the types and how many there are of each.

(a)

(b)

(c)

(d)

(e)

Cl

Cl

Cl

Cl

Cl

Cl

Cl

Cl

Cl

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4. Give the MO diagram for the following diatomic and polyatomic molecules, indicating the bond order, magnetic properties, HOMO(s) and LUMO(s).

(a) NO+ (note: the 2s and 2p orbitals for each atom are close enough in energy to mix).

(b) C2

(c) cyclic H4

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(d) linear H4

(e) Which do you think is more stable, linear or cyclic H4, and why?