Question

Why cu is smaller when compared to na?

Answer 1

Atomic no.of cu atom is 29

Electronic configuration 2 8 8 8 3

Atomic no. of Na atom 11

Electronic configuration. 2 8 1

As u can see there is increase in charge so in cu electrons appearance more electrostatic force of attraction by protons.therefore electrons tends to get attracted towards center contracting the atom and making it smaller in size as compared to Na atom.

Morever as we move from left to right in period the size of atom decreases.