Question

What is the chemical formula of Hydrogen sulphide?
(a) \[HS\]
(b) \[{{H}_{2}}S\]
(c) \[H{{S}_{2}}\]
(d) \[{{H}_{2}}{{S}_{3}}\]

Answer 1

Hint: Attempt this question by taking into account the number of valence electrons in each atom of the given compound. Try to stabilise each element by making the electronic configuration equal to its nearest noble gas.

Complete step by step answer:
Hydrogen will be most stable if its outermost shell has two electrons, i.e. the electronic configuration of its nearest noble gas, i.e. Helium.
Sulphur will be most stable if its outermost shell has eight electrons, i.e. the electronic configuration of its nearest noble gas, i.e. Argon.
Hydrogen has a configuration - \[1{{s}^{1}}\]
Sulphur has a configuration - \[1{{s}^{2}}2{{s}^{2}}2{{p}^{6}}3{{s}^{2}}3{{p}^{4}}\]
As we can see, Hydrogen has only 1 electron in its valence shell; it needs one more electron to complete its duet to achieve stability.
Also, Sulphur has only 6 electrons in its valence shell, it needs two more electrons to complete its octet to achieve stability.
Therefore, we can conclude that One atom of Sulphur will combine with two atoms ofHydrogen to make \[{{H}_{2}}S\] .

Therefore, the answer is option (b) - \[{{H}_{2}}S\]

Additional Information:
The shape of \[{{H}_{2}}S\] is bent due to the presence of lone pairs in Sulphur, which leads to repulsion and hence a bent shape of the compound.

Note: Hydrogen sulphide has a characteristic rotten egg smell. It is a very corrosive, toxic and flammable gas. It is denser than air. It is very widely used in the qualitative analysis of metal ions.