Question

What element in the second period has the largest atomic radius?

Answer 1

Why, lithium.

Explanation:

We look at `Li`, `Z=3`, versus `Ne`, `Z=10`.

As scientists we should always consider the data . The atomic radius of `Li` `=` `167xx10^-12 m`; the atomic radius of `Ne` `=` `38xx10^-12 m`.

This is quite a stunning decrease in radius. Atomic radii decrease ACROSS the Period going from left to right due to increased NUCLEAR CHARGE. As `Z` increases sequentially, the effective nuclear charge increases as the electrons, adding to the same shell, shield each other VERY imperfectly, and atomic radii contract.