Vertical trends
The usual decrease of ionization energy down a group is reflected in the trend in the direction of metallic elements in the p block. Other change is the usual increase in radius of atoms down a group, which permits a higher coordination number. Occasionally this is reflected in the changing stoichiometry of stable compounds: so ClF3, BrF5 and IF7 are the highest fluorides well-known for elements of group 17. In another groups the stoichiometry is fixed but the structure changes: so the coordination of the metallic element by fluorine is four in BeF2, 6 in MgF2 and eight in CaF2.
Even though exceptions take place this is a general trend irrespective of distinct modes of bonding. One additional general characteristic of vertical trends is significant and reflects the analogous trends in atomic properties. For each block (s, p, d) the first series involved has rather distinct chemistry compared with subsequent ones. Hydrogen (1s) is non-metallic and extremely different from the other s-block elements. The 2p-series elements (B-F) have some peculiarities not shared with the rest of the p block (e.g. a limitation in the number of valence-shell electrons in molecules and the frequent formation of multiple bonds;. In the d block, the elements of the 3d series also depict characteristic variations from the 4d and 5d series (example forming many more compounds with unpaired electrons;).