In general, what is the trend in atomic radius as atomic number increases in a vertical column on the periodic table?

In general, the trend in atomic radius as the atomic number in a vertical column of the periodic table increases is to increase.

Explanation:

The atomic radius represents the distance between the nucleus and the valence shell (that is, the outermost). By means of the atomic radius it is possible to determine the size of the atom.

In groups, the atomic radius increases with the atomic number, that is, down a column. This is because as the atomic number of the elements in a group increases, the number of occupied levels increases, while the effective nuclear charge on the outermost electron is the same. Consequently, the atomic radius increases.

In other words, when you go down in a group (column) of the periodic table, the effective nuclear charge increases, but the number of electrons added with respect to the previous element, the same group increases in a complete shell. The effect of adding new electronic shells is predominant, so they are increasingly distant from the atomic nucleus and the atomic radius is greater when you go down in a group.

So the increase in atomic radius as you go down in a group is due to the increase in electron shells.

c (diamond),

sio2 (quartz)