Assignment 02 A
1- Sketch an MO diagram to describe the bonding in [He2]2+. From the result, you can say that:
a)
b)
c)
d)
the ion is paramagnetic
the ion has a bond order of zero
the ion is likely to be less stable than He2
the ion is diamagnetic
2- Sketch an MO diagram for O2. Using the information in the diagram, which statement is
incorrect?
a)
b)
c)
d)
O2 is diamagnetic
The bond order in O2 is 2
The bonding in O2 has a π-component.
The bonding in O2 has a σ-component.
3- Which of the following molecules is non-polar?
a)
b)
c)
d)
BCl3
SO2
H2S
OF2
4- For which of the following molecules would VSEPR theory predict a trigonal pyramidal
structure?
a)
b)
c)
d)
PF3
BF3
ClF3
BrF3
5- The correct ordering of the electronegativities of the following atoms is:
a)
b)
c)
d)
N<O<H
H<N<O
H<O<N
O<N<H
6- Select the better choice in each of the following, and explain your selection briefly:
a. Higher ionization energy: Ca or Sr
b. Higher ionization energy: Mg or Al
c. Higher electron affinity: C or N
7- Use the Lewis structure model to deduce the type of nitrogen–nitrogen bond present in
(a) N2H4 , (b) N2F4, (c) N2F2 and (d) [N2H5]+.
(a) single , (b) single, (c) double (d) single
8- Determine the shapes of each of the following molecules and then, using the data in Table 2 .2,
state whether each i s expected to be polar or not: ( a) H2S; (b) CO2; (c) SO2; (d) BF3;
(e) PF3; (f) cis- N2F2; (g) trans-N2F2; (h) HCN.
( a) bent, polar; (b)linear, nonpolar; (c) bent, polar; (d) trigonal planar, nonpolar;
(e) trigonal pyramidal, polar; (f) planar, polar; (g) planar, nonpolar; (h) linear, polar.
9- (a) Use MO theory to determine the bond order in each of [He2]+ and [He2]2+.
(b) Does the MO pictur e of the bonding in these ions sugg est that they a re viab le species?
(a) 1/2, 1; (b) yes (H2 and [He2]2+ are isolectronic)
10- Account for each of the following observations.
(a) IF5 is a polar molecule.
(square pyramidal molecule)
(b) The first ionization energy of K is lower than that of Li.
(4s electron in K better shielded from nuclear charge).
(c) BI3is trigonal planar while PI3is trigonal pyramidal in shape. (BI3 has no lone pair).