What is the trend in atomic radius from left to right on the periodic table?

1 Answer
Nov 23, 2015

Atomic size decreases across a Period, and increases down a Group.

Explanation:

What are the reasons for the decrease? As nuclear charge, $Z$, increases sequentially, an electron is added to the same shell. The result is that atomic size decreases substantially, as for a single shell nuclear charge wins over electron-electron repulsion. The completion of a electronic shell helps to shield the nucleus. For the 2nd Period, the lithium atom (152 pm) is the largest atom, and the neon atom (71 pm) is the smallest (1 pm $=$ $1 \times {10}^{- 12} m$).