Chapter 7

Place the following ions in order of decreasing size: \(\mathrm{K}^{+}, \mathrm{Cl}^{-}, \mathrm{S}^{2-},\) and \(\mathrm{Ca}^{2+}\)

A The following are isoelectronic species: \(\mathrm{Cl}^{-}, \mathrm{K}^{+}\) and \(\mathrm{Ca}^{2+}\). Rank them in order of increasing (a) size, (b) ionization energy, and (c) electron attachment enthalpy.

Compare the elements \(\mathrm{Na}, \mathrm{B}, \mathrm{Al},\) and \(\mathrm{C}\) with regard to the following properties: (a) Which has the largest atomic radius? (b) Which has the most negative electron attachment enthalpy? (c) Place the elements in order of increasing ionization energy.

A Two elements in the second transition series (Y through Cd) have four unpaired electrons in their \(3+\) ions. What elements fit this description?

Answer the questions below about the elements \(A\) and \(\mathrm{B},\) which have the ground state electron configurations shown. $$ \mathrm{A}=[\mathrm{Kr}] 5 s^{2} \quad \mathrm{B}=|\mathrm{Kr}| 4 d^{10} 5 s^{2} 5 p^{5} $$ (a) Is element \(A\) a metal, nonmetal, or metalloid? (b) Which element has the greater ionization energy? (c) Which element has a larger atomic radius? (d) Which element has the more negative electron attachment enthalpy? (e) Which is more likely to form a cation? (f) What is a likely formula for a compound formed between A and B?

Why is the radius of \(L i^{+}\) so much smaller than the radius of Li? Why is the radius of \(F^{-}\) so much larger than the radius of \(\mathrm{F} ?\)

Which ions in the following list are not likely to be found in chemical compounds: \(\mathbf{K}^{2+}, \mathbf{C s}^{+}, \mathbf{A} \mathbf{l}^{4+}, \mathbf{F}^{2-}\) and \(\mathrm{Se}^{2-}\) ? Explain briefly.

Answer the following questions about first ionization energies. (a) Generally ionization energies increase on proceeding across a period, but this is not true for magnesium \((738 \mathrm{kJ} / \mathrm{mol})\) and aluminum \((578 \mathrm{kJ} / \mathrm{mol}) .\) Explain this observation. (b) Explain why the ionization energy of phosphorus \((1012 \mathrm{kJ} / \mathrm{mol})\) is greater than that of sulfur \((1000 \mathrm{kJ} / \mathrm{mol})\) when the general trend in ionization energies in a period would predict the opposite.

The bond lengths in \(\mathrm{Cl}_{2}, \mathrm{Br}_{2},\) and \(\mathrm{I}_{2}\) are 200,228 and \(266 \mathrm{pm},\) respectively. Knowing that the tin radius is \(141 \mathrm{pm},\) estimate the bond distances in \(\mathrm{Sn}-\mathrm{Cl}, \mathrm{Sn}-\mathrm{Br},\) and \(\mathrm{Sn}-\mathrm{I} .\) Compare the estimated values with the experimental values of 233,250 and \(270 \mathrm{pm},\) respectively.

Write electron configurations to show the first two ionization processes for potassium. Explain why the second ionization energy is much greater than the first.

What is the trend in ionization energy when proceeding down a group in the periodic table. Rationalize this trend.

(a) Explain why the sizes of atoms change when proceeding across a period of the periodic table. (b) Explain why the sizes of transition metal atoms change very little across a period.

Which of the following elements has the greatest difference between its first and second ionization energies: \(\mathrm{C}, \mathrm{Li}, \mathrm{N},\) Be? Explain your answer.

A What arguments would you use to convince another student in general chemistry that \(\mathrm{MgO}\) consists of the ions \(\mathrm{Mg}^{2+}\) and \(\mathrm{O}^{2-}\) and not the ions \(\mathrm{Mg}^{+}\) and \(\mathrm{O}^{-2}\). What experiments could be done to provide some evidence that the correct formulation of magnesium oxide is \(\mathrm{Mg}^{2+} \mathrm{O}^{2-} ?\)

Explain why the first ionization energy of Ca is greater than that of \(K\), whereas the second ionization energy of Ca is lower than the second ionization energy of K.

A The ionization energies for the removal of the first electron in \(\mathrm{Si}, \mathrm{P}, \mathrm{S},\) and \(\mathrm{Cl}\) are as listed in the table below. Briefly rationalize this trend.

Using your knowledge of the trends in element sizes on going across the periodic table, explain briefly why the density of the elements increases from K through V.

The discovery of two new elements (atomic numbers 113 and 115 ) was announced in February 2004. (a) Use spáf and noble gas notations to give the electron configurations of these two elements. (b) For each of these elements, name another element in the same periodic group. (c) Element 113 was made by firing the nucleus of a light atom at a heavy americium atom. The two nuclei combine to give a nucleus with 113 protons. What light atom was used as a projectile?

Explain why the reaction of calcium and fluorine does not form \(\mathrm{CaF}_{3}\)

Sodium metal reacts readily with chlorine gas to give sodium chloride. $$ \mathrm{Na}(\mathrm{s})+1 / 2 \mathrm{C}_{2}(\mathrm{g}) \rightarrow \mathrm{NaCl}(\mathrm{s}) $$ (a) What is the reducing agent in this reaction? What property of the element contributes to its ability to act as a reducing agent? (b) What is the oxidizing agent in this reaction? What property of the element contributes to its ability to act as an oxidizing agent? (c) Why does the reaction produce NaCl and not a compound such as \(\mathrm{Na}_{2} \mathrm{Cl}\) or \(\mathrm{NaCl}_{2} ?\)