- As one moves down the alkali metal column, nuclear charge increases.
- As one moves down the alkali metal column, the electron cloud would be expected to
get larger due to higher energy levels being filled. - As one moves down the alkali metal family, the charge density would be expected to
decrease due to significantly larger volume and more shielding. - As one moves down the alkali metal family, one would expect the attractive forces
holding the crystal structure together to decrease due to this last factor. - Boiling point and melting point would be expected to be comparable because they
both are functions of the strength of intermolecular attractive forces.
(c)Restatement: Rank Cs, Li, KCl, I 2 , and F 2 in order of decreasing melting point.
Explain.
- #1 KCl — highest melting point. Ionic bond present—formed by the transfer of
electrons. - #2 Li — alkali metal. Metallic bonds present (cations, mobile electrons). Low-den-
sity metal. - #3 I 2 — solid at room temperature. Covalent bond present. Nonpolar.
- #4 Cs — liquid at near room temperature. Metallic bonds present; however, due to
low charge density as explained above, attractive forces are very weak. - #5 F 2 — gas at room temperature. Covalent bonds present. One would expect a
smaller electron cloud than in I 2 due to reasons stated above.
Covalent Bonding