Question

if the K and L shells of an atom are full and the M shell has 2 electrons then what is the atomic number of the atom.​

Answer 1

18 is the atomic number of the atom.

[because k shell has 2 electrons.L shell has 8 electrons.so 2+8=10.now M shell has 2 electrons so 10+2=12]

The number of electrons is equal to the number of protons.

Answer 2

Answer:

$\huge{ \green{12 \: (Magnesium)}}$

Explanation:

K and L shell can have at most 2 , 8 electrons and M has 2 electrons . So total no. of electrons

$= 2 + 8 + 2 = 12$

[ Note : General formula for electrons in nth shell is

$= 2 {n}^{2}$

]