Question

What is a molecule?
(a)- A group of two or more atoms that are chemically bonded together or are tightly held together by attractive forces.
(b)- Smallest particle of the matter
(c)- Mass unit equal to exactly one-twelfth the mass of a carbon-12 atom
(d)- The combining power (or capacity) of an element

Answer 1

Suppose ${{H}_{2}}$, in which two hydrogen atoms are bonded with each other with the help of a covalent bond, is called a hydrogen molecule. ${{S}_{8}}$, in which eight sulfur molecules are bonded with each to form a sulfur molecule.

Complete step by step answer:
When the atoms combine by intermolecular forces or bonds like a covalent bond, ionic bond, coordination bond, etc form molecules. We can classify the molecules into two types: Molecules of elements and Molecules of the compound.
Molecules of elements: We can also call Molecules of elements as homoatomic or homonuclear because only one type of atom is involved in the formation of a molecule, but the atoms can be of any number. For example, hydrogen molecule (${{H}_{2}}$), oxygen molecule (${{O}_{2}}$), ozone (${{O}_{3}}$), phosphorus molecule (${{P}_{4}}$), sulfur molecule (${{S}_{8}}$).
Molecules of compounds: We can also call Molecules of the compound as heteroatomic or heteronuclear because more than one type of atom is involved in the formation of molecules. For example, hydrogen chloride ($HCl$), water (${{H}_{2}}O$), carbon dioxide ($C{{O}_{2}}$), ammonia ($N{{H}_{3}}$) etc.

So, the correct answer is an option (a)- A group of two or more atoms that are chemically bonded together or are tightly held together by attractive forces.

Note: (b)- Smallest particle of the matter: atom
(c)- Mass unit equal to exactly one-twelfth the mass of a carbon-12 atom: One atomic mass unit.
(d)- The combining power (or capacity) of an element: Atomicity.