What do the elements in the Carbon Group (group 14) have in common (besides the number of valence electrons)?

Answer 1

Each of the elements in this group has 4 electrons in its outer energy level. The last orbital of all these elements is the p2 orbital. In most cases, the elements share their electrons. The tendency to lose electrons increases as the size of the atom increases, as it does with increasing atomic number. Carbon alone forms negative ions, in the form of carbide (C4-) ions. Silicon and germanium, both metalloids, each can form +4 ions. Tin and lead both are metals while ununquadium is a synthetic shortlived radioactive metal.

Answer 2

Very little. This is the group which shows the biggest change from non-metallic to metallic behaviour, so the elements have very little in common. I suppose the answer that is expected is that they all show an oxidation state of +4 (a valency of 4).