1. How will you find the valency of chlorine, sulphur and magnesium?

To find the valency of chlorine:

The atomic number of chlorine is 17

Number of electrons is equal to the number of protons in chlorine i.e., 17

The distribution of electrons in chlorine atom is K-2, L-8, M-7

Hence, from the distribution of chlorine it is clear that to fill the M shell only one electron is required. Therefore its valency is -1.

To find the valency of sulphur:

The atomic number of sulphur is 16

Number of electrons is equal to the number of protons in sulphur i.e., 16

The distribution of electrons in sulphur atom is K-2, L-8, M-6

Hence, from the distribution of sulphur it is clear that to fill the M shell two more electrons are required. Therefore its valency is -2.

To find the valency of magnesium:

The atomic number of magnesium is 12

Number of electrons is equal to the number of protons in magnesium i.e., 12

The distribution of electrons in magnesium atom is K-2, L-8, M-2

Hence, from the distribution of magnesium it is clearly evident that to fill the M shell six more electrons are required. But it will be difficult to gain 6 electron. So, it will loss two electrons instead.

Thus, its valency is +2.