Lewis's theory is satisfactory to explain bonding in the ionic compound $\mathrm{K}_2 \mathrm{O}$, but it does not readily explain the formation of the ionic compounds potassium superoxide, $\mathrm{KO}_2$, and potassium peroxide, $\mathrm{K}_2 \mathrm{O}_2$ (a) Show that molecular orbital theory can provide this explanation.

The Lewis structure of $\mathrm{N}_2$ indicates that the nitrogen-to-nitrogen bond is a triple covalent bond. Other evidence suggests that the $\sigma$ bond in this molecule involves the overlap of $s p$ hybrid orbitals. (a) Draw orbital diagrams for the $\mathrm{N}$ atoms to describe the bonding in $\mathrm{N}_2$.

Explain why the solar cell in Figure 11-40 operates over a broad range of wavelengths rather than at a single wavelength (often the case when quantum effects are involved)?

The energy gap, $\Delta E$, for silicon is $110 \mathrm{~kJ} / \mathrm{mol}$. What is the minimum wavelength of light that can promote an electron from the valence band to the conduction band in silicon? In what region of the electromagnetic spectrum is this light?

Explain why the electrical conductivity of a semiconductor is significantly increased if trace amounts of either donor or acceptor atoms are present, but is unchanged if both are present in equal number.

The effect of temperature change on the electrical conductivity of ultrapure silicon is quite different from that on silicon containing a minute trace of arsenic. Why is this so?

Explain whether the addition of gallium arsenide in trace amounts to germanium, would produce a $n$-type semiconductor.

Explain whether the addition of arsenic in trace amounts to germanium, would produce a $n$-type semiconductor.

Explain whether the addition of cadmium sulfide in trace amounts to germanium, would produce a $n$-type semiconductor.

Explain whether the addition of tin in trace amounts to germanium, would produce a $n$-type semiconductor.

Explain whether the addition of aluminium in trace amounts to germanium, would produce a $n$-type semiconductor.

Construct the molecular orbital diagram for SrCl. Would you expect the bond length of SrCl$^+$ to be longer or shorter than that of SrCl?

Explain whether the addition of sulfur in trace amounts to germanium, would produce a $n$-type semiconductor.

Explain whether the addition of gallium in trace amounts to silicon, would produce a $p$-type semiconductor.