The element which has a total of two shells and has three electrons in its valence shell is

The correct option is B

$\mathrm{B}$

The explanation for the correct option:

Number of valence electrons in the valence shell = 3

• Number of valence electrons + 10= Number of group

So, the element belongs to group 13.

Number of shells = 2

• Number of shells = Number of period

So, the element belongs to period 2.

Therefore, the element that has total of two shells and three electrons in valence shell is Boron ($\mathrm{B}$).

The explanation for the incorrect option:

Beryllium ($\mathrm{Be}$) consists of two shells but it has four electrons in valence shell.

Aluminium ($\mathrm{Al}$) consists of three shells and three electrons in valence shell.

Magnesium ($\mathrm{Mg}$) consists of three shells and has two electrons in valence shell.

Final answer:

Hence, option (B) is the correct option.