Question

In one molecule of ammonium sulphide , there are
A.2 atoms of $N$ , 8 atoms of $H$ and 1 atom of $S$
B.1 atom of $N$ , 4 atoms of $H$ and 1 atom of $S$
C.1 atom of $N$ , 4 atoms of $H$ and 2 atoms of $S$
D.2 atoms of $N$ , 8 atoms of $H$ and 2 atoms of $S$

Answer 1

According to the law of definite proportions , a chemical compound is always found to be made up of the same elements combined together in the same fixed proportion by mass .

Complete step by step answer:
Chemical formula of a compound tells us the whole number ratio between the elements in the compound.
It is represented by the symbols of the elements present in the compound along with the number of atoms of each element written in the subscript.
The number of atoms of each element is governed by the valency of each atom, that is the combining capacity of an atom.
The valency of an element is related to the number of electrons present in the outer shell or valence shell.
For elements having one, two, three or four electrons in the valence shell, the valency is equal to the number of valence electrons.
For elements having five, six, seven or eight electrons in the valence shell, the valency is equal to (8-number of valence electrons).
For , ammonium sulphide,
we know that the valency of sulphide ion is -2 (it gains two electrons to complete its octet ) while that of ammonium ion is +1 ( there are 4 hydronium ions attached to nitrogen )
Hence, the chemical formula of the compound becomes ${(N{H_4})_2}S$ .
This means the compound contains 2 atoms of $N$ , 8 atoms of $H$ and 1 atom of $S$ .

Therefore, option A is correct.

Note: We know that ammonium sulphide is a neutral molecule , so just by knowing the valency of all the elements present in this compound we can find the number of atoms of each element present in the compound .