Chapter 18: The Representative Elements

The United States Public Health Service (USPHS) recommends the fluoridation of water as a means for preventing tooth decay. The recommended concentration is $\mathbf{1}\mathit{m}\mathit{g}{\mathit{F}}^{\mathbf{-}}\mathbf{/}\mathit{L}\mathbf{.}$. The presence of calcium ions in hard water can precipitate the added fluoride. What is the maximum molarity of calcium ions in hard water if the fluoride concentration is at the USPHS recommended level?$\left(K_{sp}forCa{F}_2=4.0\times {10}^{-11}\right)$

Although the earth was formed from the same interstellar material as the sun, there is little hydrogen in the earth's atmosphere. How can you explain this?

Slaked lime $\left[{\text{Ca(OH)}}_{\text{2}}\right]$is used to soften hard water by removing calcium ions from hard water through the reaction

${\mathbf{\text{Ca(OH)}}}_{\mathbf{\text{2}}}{\mathbf{\text{(aq) + Ca}}}^{\mathbf{\text{2 +}}}\mathbf{\text{(aq) + 2HC}}{{\mathbf{\text{O}}}_{\mathbf{\text{3}}}}^{\mathbf{\text{-}}}\mathbf{\text{(aq)}}\mathbf{\to }$${\mathbf{\text{2CaCO}}}_{\mathbf{\text{3}}}{\mathbf{\text{(s) + 2H}}}_{\mathbf{\text{2}}}\mathbf{\text{O(l)}}$

Although ${\mathbf{\text{CaCO}}}_{\mathbf{\text{3}}}\mathbf{\text{(s)}}$is considered insoluble, some of it does dissolve in aqueous solutions. Calculate the molar solubility of ${\mathbf{\text{CaCO}}}_{\mathbf{\text{3}}}\mathbf{\text{(s)}}$in water$\left(K_{sp}=8.7\times {10}^{-9}\right)$

What is the valence electron configuration for the Group $\mathbf{3}\mathit{A}$elements? How does metallic character change as one goes down this group? How are boron and aluminium different?

What are three-centered bonds?

Boron hydrides were once evaluated for possible use as rocket fuels. Complete and balance the following equation:

${\text{B}}_2{\text{H}}_6+{\text{O}}_2\to \text{B}(\text{OH}{)}_3$

Consider element $\mathbf{113}$. What is the expected electron configuration for element$\mathbf{113}$? What oxidation states would be exhibited by element$\mathbf{113}$in its compounds?

Write equations describing the reactions of Ga with each of the following: ${\mathit{F}}_{\mathbf{2}}$,${\mathit{O}}_{\mathbf{2}}$,${\mathbf{\text{S}}}_{\mathbf{8}}$, and$\mathit{H}\mathit{C}\mathit{l}$.

Thallium and indium form $\mathbf{+}\mathbf{1}$ and$\mathbf{+}\mathbf{3}$ oxidation states when in compounds. Predict the formulas of the possible compounds between thallium and oxygen and between indium and chlorine. Name the compounds.

$\mathit{A}{\mathit{l}}_{\mathbf{2}}{\mathit{O}}_{\mathbf{3}}$is amphoteric. What does this mean?