a) The electron configuration of \(X\) (sodium) is:
\[ 1s^2 2s^2 2p^6 3s^1 \]
Sodium is located in:
- Period: 3
- Group: 1
- Block: s-block
\(\boxed{\text{Period: 3, Group: 1, Block: s-block}}\)
b) Sodium (Na) is an s-block element and is classified as a metal.
\(\boxed{\text{s-block, metal}}\)