Explanation:
Magnesium has atomic number 12. It will be distributed in K, L, M shell in the following way:
K shell can accommodate a maximum of 2 electrons.
L shell can accommodate a maximum of 8 electrons and
M shell will accommodate 2 electrons
So the configuration becomes 2, 8,3
The density of the stone is 5 because the formula is mass/volume and the volume is 5 and the mass is 25
