Question

The element sulphur has atomic number 16 and mass number 32. Calculate the number of electrons, protons, and neutrons in the ion formed. Represent the ion. What will be its va­lency?

Answer 1

Given:

Atomic number of Sulphur $\mathbf{\left(}\mathbf{S}\mathbf{\right)}$$=16$

Mass number of Sulphur $\mathbf{\left(}\mathbf{S}\mathbf{\right)}$$=32$

Formula used:

1. Atomic number$=$Number of electrons$=$Number of protons
2. Mass number$=$Number of protons$+$Number of neutrons

Formation of ion formed from Sulhur atom:

1. The atomic number of Sulphur is $16$. Thus, its electronic configuration is $(2,8,6)$.
2. A Sulphur atom gains two electrons in the outermost shell and forms a Sulphide ion.
3. Thus, for a Sulphide ion, the number of protons and neutrons is same as that of Sulphur atom but number of electrons increases by two.

Representation of Sulphide ion:

1. The sulphide ion has two units of negative charges.
2. Thus, Sulphide ion is represented as $S^{2-}$.

Valency of Sulphide ion:

1. The combining capacity of the atom of an element with the atoms of other elements in order to acquire eight electrons in its outermost shell is known as valency.
2. The sulphide ion has gained two electrons to acquire eight electrons in its outermost shell.
3. Thus, the valency of Sulphide ion is $2$.

Calculate the number of electrons in Sulphide ion $\left(S^{2-}\right)$:

Number of electrons in Sulphide ion$=$Number of electrons in Sulphur atom$+2$

Number of electrons in Sulphur atom$=$Atomic number$=16$

Thus,

Number of electrons in Sulphide ion$=16+2=18$

Calculate the number of protons in Sulphide ion $\left(S^{2-}\right)$:

Number of protons in Sulphide ion$=$Number of protons in Sulphur atom$=$Atomic number

Number of protons in Sulphide ion$=16$

Calculate the number of neutrons in Sulphide ion $\left(S^{2-}\right)$:

Mass number$=$Number of protons$+$Number of neutrons

Thus,

Number of neutrons$=$Mass number$-$Number of protons

Number of neutrons$=32-16$

Number of neutrons$=16$

Thus, number of neutrons in Sulphide ion are $16$.