Chapter 7

Arrange the following isoelectronic species in order of increasing ionization energy: \(\mathrm{O}^{2-}, \mathrm{F}^{-}, \mathrm{Na}^{+}, \mathrm{Mg}^{2+}\).

Write the empirical (or molecular) formulas of compounds that the elements in the third period (sodium to chlorine) should form with (a) molecular oxygen and (b) molecular chlorine. In each case indicate whether you would expect the compound to be ionic or molecular in character.

$$ \begin{aligned} &\text { Arrange the following species in isoelectronic pairs: }\\\ &\mathrm{O}^{+}, \mathrm{Ar}, \mathrm{S}^{2-}, \mathrm{Ne}, \mathrm{Zn}, \mathrm{Cs}^{+}, \mathrm{N}^{3-}, \mathrm{As}^{3+}, \mathrm{N}, \mathrm{Xe} \end{aligned} $$

In which of the following are the species written in decreasing order by size of radius: (a) Be, Mg, Ba, (b) \(\mathrm{N}^{3-}, \mathrm{O}^{2-}, \mathrm{F}^{-}\) (c) \(\mathrm{Tl}^{3+}, \mathrm{Tl}^{2+}, \mathrm{Tl}^{+} ?\)

Which of the following properties show a clear periodic variation: (a) first ionization energy, (b) molar mass of the elements, (c) number of isotopes of an element, (d) atomic radius?

When carbon dioxide is bubbled through a clear calcium hydroxide solution, the solution appears milky. Write an equation for the reaction, and explain how this reaction illustrates that \(\mathrm{CO}_{2}\) is an acidic oxide.

You are given four substances: a fuming red liquid, a dark metallic-looking solid, a pale-yellow gas, and a yellow-green gas that attacks glass. You are told that these substances are the first four members of Group 7A, the halogens. Name each one.

For each pair of elements listed, give three properties that show their chemical similarity: (a) sodium and potassium and (b) chlorine and bromine.

What is the most reactive element on the periodic table?

Explain why the first electron affinity of sulfur is \(200 \mathrm{~kJ} / \mathrm{mol}\) but the second electron affinity is \(-649 \mathrm{~kJ} / \mathrm{mol}\).