Question

Smallest particles of matter which cannot be further divided are called:
(A) molecules
(B) objects
(C) atoms
(D) none of these

Answer 1

Hint: An elaborate study of particles of matter was done by John Dalton. The postulates given by Dalton called Dalton's atomic theory talks about particles and also about the smallest unit of matter. Try to recall the postulates to understand the meaning of molecules and atoms and which is the smallest unit of matter.

Complete step by step answer:
John Dalton published his theory about atoms in the year 1808. His postulates were mainly based on the two laws of chemical combination namely, conservation of mass and constant proportion.
The postulates of Dalton's atomic theory are :
- Every matter consists of indivisible particles called atoms
- Atoms of the same element that will have same shape and mass irrespective of the source from where it is obtained
- Atoms can neither be destroyed nor created
- Atoms of different elements may combine with each other in a simple and fixed ratio to form compounds
- Atoms of the same element may combine in more than one ratio with the fixed mass of the second element to form more than one type of compound
- The atom is the smallest unit of matter that can take part in any chemical reaction
From the above postulates we can conclude that the smallest particles of matter which cannot be further divided are atoms.
So, the correct answer is “Option C”.

Note: Although the fact that the smallest unit of matter that can take part in a chemical reaction is atom is true, atom is no longer considered the smallest particle of matter. This is because after Dalton's atomic theory, atomic sub particles like electrons, protons and neutrons were discovered which are now considered basic units of matter.