27.1 General aspects and trends in the p block
• Most p-block elements can adopt more than one oxidation state, and they
normally vary in units of 2.
• Group 13 compounds act as Lewis acids, as can compounds of Group 14 and
15 if they contain elements of the third period or lower.
• Group 15, 16, and 17 compounds have lone pairs, so they can act as Lewis
bases, but the strength of the base depends on the type of orbital the electron
pair is in.
Trends across the periods of the p block
• The metallic character of an element decreases from left to right across a
period of the p block due to increasing ionization enthalpies.
• The maximum oxidation state increases across a period, though expansion of
the octet is not possible for the second period elements.
• The ionic character of the oxides and halides decreases across each period.
• The acidic character of the oxides increases across each period.