91Ó°ÊÓ

State whether the representative particle in each of the following substances is an atom, a molecule, or a formula unit: (a) uranium, U (b) fluorine, \(\mathrm{F}_{2}\) (c) uranium hexafluoride, UF \(_{6}\) (d) hydrogen fluoride, HF

Write formula units by combining the cations and anions in each of the following pairs: (a) \(\mathrm{Sr}^{2+}\) and \(\mathrm{As}^{3-}\) (b) \(\mathrm{Ra}^{2+}\) and \(\mathrm{O}^{2-}\) (c) \(\mathrm{Al}^{3+}\) and \(\mathrm{CO}_{3}^{2-}\) (d) \(\mathrm{Cd}^{2+}\) and \(\mathrm{OH}^{-}\)

Write formula units by combining the cations and anions in each of the following pairs: (a) \(\mathrm{Sc}^{3+}\) and \(\mathrm{N}^{3-}\) (b) \(\mathrm{Ti}^{4+}\) and \(\mathrm{O}^{2-}\) (c) \(\mathrm{NH}_{4}^{+}\) and \(\mathrm{CO}_{3}^{2-}\) (d) \(\mathrm{Hg}_{2}{ }^{2+}\) and \(\mathrm{PO}_{4}{ }^{3-}\)

Explain why the radius of a sodium ion \((0.095 \mathrm{nm})\) is about half that of a sodium atom \((0.186 \mathrm{nm})\).

Explain why the radius of a chloride ion \((0.181 \mathrm{nm})\) is about twice that of a chlorine atom \((0.099 \mathrm{nm})\).

Label the polar Ge \(-\) Cl bond using delta notation \(\left(\delta^{+}\right.\) and \(\delta^{-}\) ).

Write the electron dot formula and draw the structural formula for silane, \(\operatorname{SiH}_{4},\) whose central atom is a semimetal.

Write the electron dot formula and draw the structural formula for the arsenate ion, \(\mathrm{AsO}_{3}^{3-},\) whose central atom is a semimetal.

Write the electron dot formula and draw the structural formula for the silicate ion, \(\mathrm{SiO}_{3}^{2-},\) whose central atom is a semimetal.

Predict the electron pair geometry, the molecular shape, and the bond angle for a carbon disulfide molecule, \(\mathrm{CS}_{2}\), using VSEPR theory.