Question

Which of the following pairs of atomic numbers represents elements belong to the same group?

• A. 11,20
• B. 12, 30
• C. 13, 31
• D. 14, 33

Answer 1

The correct option is C 13, 31

valence shell configuration of element $(Z=13)=3s^{2}3p^1$
$Z=31=4s^{2}4p^1$