Question

How many atoms are present in a \[{{\text{H}}_2}{\text{S}}\] molecule?

Answer 1

Hint: The molecular formula of a compound itself describes the types of element present in it with their number in subscript. This can be used to determine the number of atoms of an element present in the given compound.

Complete answer:
An atom is the smallest particle of the element that can exist independently and retain all its properties. A molecule is the smallest particle of an element or a compound capable of independent existence under ordinary conditions. It shows all the properties of the substance. A chemical formula of a compound shows its constituent elements and the number of atoms of each combining element.
According to the Law of constant proportions by Proust, it states that in a chemical substance the elements are always present in definite proportions by mass. For example molecules of water \[{{\text{H}}_2}{\text{O}}\] prepared from any source contains hydrogen and oxygen in the ratio of 1:8 by mass.
For example a molecule of water \[{{\text{H}}_2}{\text{O}}\] , if we analyze; it has two atoms of hydrogen combined with one atom of oxygen. As the mass of each atom of hydrogen is 1 amu and mass of each atom of oxygen is 16 amu which corresponds to the mass of one molecule of \[{{\text{H}}_2}{\text{O}}\] to be 18 amu. Now as given according to the question, \[{{\text{H}}_2}{\text{S}}\] molecule, if we analyze it has two atoms of hydrogen combined with one atom of sulphur. The mass of one molecule of \[{{\text{H}}_2}{\text{S}}\] is 34 amu as mass of two hydrogen atom weight 4 amu and mass of one atom of sulphur weight 32 amu.
Thus, there are in total 3 atoms present in a molecule of \[{{\text{H}}_2}{\text{S}}\] in which two atoms are of hydrogen element and one is of sulphur element.

Note:
Generally mass of one atom, molecule or compound is expressed in terms of atomic mass unit or amu and whereas mass of moles of atom, molecule or compound are expressed in terms of gram.