Question

The size of an atom generally increases in what direction on the periodic table?

Answer 1

Atomic size decreases across a Period (from our left to our right), but increases down a Group.

Explanation:

Of course I should qualify these statements.

As we face the table, atomic size decreases across from left to right on the same Period; in incomplete valence shells atomic charge is shielded very imperfectly.

Once a valence shell is complete, a new shell is begun at a larger radius, and the process of atomic contraction begins again. Thus down a Group, a column on the Table, atomic size increases. As a physical scientist you should seek data that relate Periodicity with atomic size.