19.1 Representative Elements

1. 19.1 Representative Elements Nathan Medsker

2. Review • Representative Elements, chemical properties determined by s and p electrons, 1A through 8A. • Transition Metals, determined by filling of d orbitals. • Lanthanides and Actinides, determined by filling of 4f and 5f orbitals. • Metalloids exhibit both metallic and nonmetallic properties.

3. Atomic Size and Group Anomalies • Chemical properties of a group show many similarities but there are differences. • Large increase in atomic radii from first to second member of a group causes the first element to have vastly different properties. • Ex: Small Hydrogen atom has much stronger attraction for electrons and will form covalent bonds with nonmetals, while others won’t.

4. Atomic Size and Group Anomalies • Size also has an effect. • Ex: Oxides of group 2A metals are all basic except for BeO, which is amphoteric. The small Be 2+ ion can polarize the electrons of the O 2- ion, allowing for electron sharing. This reduces its ionic character and thus basicity.

5. Atomic Size and Group Anomalies • Differences in molecular bonding. • Ex: Group 4A, Carbon has C-C bonds, while Silicon is dominated by Si-O bonds, not Si-Si. It is inefficient to form π bonds so a noble gas configuration is achieved with Si-O bonds. • Explains chemical forms. • Ex: The larger P4 molecules do not form strong π bonds so form single bonds

6. Abundance and Preparation • Metallurgy: The process of obtaining a metal from its ore. • Metals in ores are found as cations, so metallurgy always involves reduction to elemental state. Carbon is the common reducing agent. Electrolysis can be used on the most active metals.

7. Abundance and Preparation • Liquefaction: A process of compressing gas and allowing remaining gas to carry off the heat until some gas becomes cool enough to form the liquid state. • Some substances can be separated through distillation due to different boiling points. (Nitrogen and Oxygen). • See charts on page 878/9.