# Question #4670c

Apr 21, 2017

Atomic number for magnesium is $12$. The nucleus contains $12 {\text{p"^+ and 12 "n}}^{\circ}$

As per Bohr's model the electrons could be arranged inside the atom as per following

• Each shell or energy level can contain only a fixed number of electrons.
• The general formula proposed by Bohr was that the ${n}^{t h}$ shell can contain up to $2 \left({n}^{2}\right)$ electrons. Where $n = 1 , 2 , 3. \ldots$ and is the shell number.
• The first shell can hold up to two electrons
• The second shell can hold up to eight electrons
• The third shell can hold up to eighteen electrons and so on.

Therefore,

First $2$ electrons will fill in the $\text{First shell } n = 1$,
Next $8$ electrons will fill in the $\text{Second Shell } n = 2$,
Remaining $2$ electrons will go in the $\text{third shell } n = 3$.