91Ó°ÊÓ

How many electrons are in the valence shells of (a) Be in \(\mathrm{BeCl}_{2},\) (b) \(\mathrm{B}\) in \(\mathrm{BCl}_{3}\), and (c) \(\mathrm{H}\) in \(\mathrm{H}_{2} \mathrm{O}\) ?

What is the minimum number of electrons that would be expected to be in the valence shell of \(\mathrm{As}\), in \(\mathrm{As} \mathrm{Cl}_{5}\) ?

Nitrogen and arsenic are in the same group in the periodic table. Arsenic forms both \(\mathrm{AsCl}_{3}\) and \(\mathrm{AsCl}_{5}\), but with chlorine, nitrogen only forms \(\mathrm{NCl}_{3}\). On the basis of the electronic structures of \(\mathrm{N}\) and \(\mathrm{As}\), explain why this is so.

What is the definition of formal charge? How are formal charges indicated on a structural formula?

How are formal charges for atoms in a molecule determined? The sum of the formal charges of a molecule must add up to what?

What are the formal charges on the atoms in the \(\mathrm{HCl}\) molecule? What are the actual charges on the atoms in this molecule? Are formal charges the same as actual charges?

What is a coordinate covalent bond?

Once formed, how (if at all) does a coordinate covalent bond differ from an ordinary covalent bond?

\(\mathrm{BCl}_{3}\) has an incomplete valence shell. Use Lewis structures to show how it could form a coordinate covalent bond with a water molecule.

What is a resonance hybrid? How does it differ from the resonance structures drawn for a molecule?