Question

If an atom of an element has 20 electrons in total, then what will be the outer most orbit of the atom and the number of valence electrons?

• A. N, 6
• B. M, 10
• C. N, 2
• D. M, 2

Answer 1

The correct option is C N, 2

The atom has 20 electrons. The electronic configuration using Bohr's rules is 2, 8, 8, 2 .

The maximum number of electrons in each shell is as follows

K-Shell will be=$2$ $\times$ $1^2$=$2$

L- Shell will be=$2$ $\times$ $2^2$ = $8$

M- Shell will be= $2$ $\times$ $3^2$ =$18$

N- Shell will be= $2$ $\times$ $4^2$= $32$

The electrons will be filled from inner orbit to outer orbit considering the maximum number of electrons for reach orbit.

So, the electronic configuration is 2, 8, 8, 2.