91Ó°ÊÓ

Which of the following molecules or ions are linear? a. \(\mathrm{SeF}_{2}\) b. \(\mathrm{CHCl}_{3}\) c. \(\mathrm{SeF}_{4}\) d. \(\mathrm{SnF}_{6}{ }^{2-}\)

Which of the following molecules or ions are trigonal planar? a. \(\mathrm{BBr}_{3}\) b. \(\mathrm{AsH}_{3}\) c. \(\mathrm{ClF}_{4}^{-}\) d. \(\mathrm{TeF}_{5}^{-}\)

Explain how the dipole moment could be used to distinguish between the cis and trans isomers of 1,2 -dibromoethene:

Two compounds have the formula \(\mathrm{Pt}\left(\mathrm{NH}_{3}\right)_{2} \mathrm{Cl}_{2}\). (Compound \(\mathrm{B}\) is cisplatin, mentioned in the opening to Chapter 1.) They have square planar structures. One is expected to have a dipole moment; the other is not. Which one would have a dipole moment?

Explain in terms of bonding theory why all four hydrogen atoms of allene, \(\mathrm{H}_{2} \mathrm{C}=\mathrm{C}=\mathrm{CH}_{2}\), cannot lie in the same plane.

What is the molecular orbital configuration of \(\mathrm{HeH}^{+}\) ? Do you expect the ion to be stable?

What is the molecular orbital configuration of \(\mathrm{He}_{2}{ }^{+}\) ? Do you expect the ion to be stable?

Calcium carbide, \(\mathrm{CaC}_{2}\), consists of \(\mathrm{Ca}^{2+}\) and \(\mathrm{C}_{2}^{2-}\) (acetylide) ions. Write the molecular orbital configuration and bond order of the acetylide ion, \(\mathrm{C}_{2}^{2-}\).

The oxygen-oxygen bond in \(\mathrm{O}_{2}{ }^{+}\) is \(112 \mathrm{pm}\) and in \(\mathrm{O}_{2}\) is \(121 \mathrm{pm}\). Explain why the bond length in \(\mathrm{O}_{2}{ }^{+}\) is shorter than in \(\mathrm{O}_{2}\). Would you expect the bond length in \(\mathrm{O}_{2}^{-}\) to be longer or shorter than that in \(\mathrm{O}_{2}\) ? Why?

The nitrogen-nitrogen bond distance in \(\mathrm{N}_{2}\) is \(109 \mathrm{pm}\). On the basis of bond orders, would you expect the bond distance in \(\mathrm{N}_{2}{ }^{+}\) to be less than or greater than \(109 \mathrm{pm} ?\) Answer the same question for \(\mathrm{N}_{2}^{-}\).