Question

Which of the following is not a postulate of Dalton's atomic theory?

• A. Different elements have atoms of different masses.
• B. Atoms combine in simple whole number ratios to form compounds.
• C. Atoms are not created or destroyed in chemical change.
• D. Atoms of a single element can have different masses.

Answer 1

The correct option is D Atoms of a single element can have different masses.

Postulates of Dalton's atomic theory:

1. All matter consists of indivisible particles called atoms.
2. Atoms of the same elements are similar in shape and mass but differ from the atoms of other elements.
   
3. Atoms cannot be created or destroyed.
   
4. Atoms of different elements may combine with each other in fixed, simple, whole-number ratios to form elements and compounds.
   
5. The atom is the smallest unit of matter that can take part in a chemical reaction.
   

'Atoms of a single element can have different masses' is not present in postulates of Dalton's atomic theory. It is in fact a limitation of Dalton's atomic theory. Hence, option D is the correct choice.