Question

The incorrect postulates of the Dalton's atomic theory are :
(A) Atoms of different elements differ in mass.
(B) Matter consists of divisible atoms.
(C) Compounds are formed when atoms of different element combine in a fixed ratio.
(D) All the atoms of given element have different properties including mass.
(E) Chemical reactions involve reorganisation of atoms.
Choose the correct answer from the options given below :

• A. (B), (D), (E) only
• B. (A), (B), (D) only
• C. (C), (D), (E) only
• D. (B), (D) only

Answer 1

The Correct Option is D

Statement (B) is incorrect because Dalton proposed that atoms are indivisible, but later discoveries (e.g., protons, electrons, neutrons) disproved this. Statement (D) is incorrect because Dalton stated that atoms of the same element are identical in all properties, including mass. Statement (E) is correct as chemical reactions involve the reorganization of atoms but do not change their nature.

Thus, the incorrect postulates are (B) and (D) only.

Answer 2

Step 1: Recall Dalton’s atomic theory postulates
Dalton proposed several postulates about atoms and matter. The main ones are:
1. Matter is made up of indivisible and indestructible atoms.
2. All atoms of a given element are identical in mass and properties.
3. Atoms of different elements differ in mass and properties.
4. Compounds are formed when atoms of different elements combine in simple, whole-number ratios.
5. Chemical reactions involve rearrangement of atoms; atoms are neither created nor destroyed.

Step 2: Analyze each given statement
(A) Atoms of different elements differ in mass.
✔ This is correct according to Dalton’s theory.

(B) Matter consists of divisible atoms.
✖ This is incorrect. Dalton said atoms are indivisible (cannot be divided further).

(C) Compounds are formed when atoms of different elements combine in a fixed ratio.
✔ This is correct — one of Dalton’s main postulates.

(D) All the atoms of a given element have different properties including mass.
✖ This is incorrect. Dalton proposed that all atoms of a given element are identical in properties and mass (though isotopes later disproved this).

(E) Chemical reactions involve reorganisation of atoms.
✔ This is correct — Dalton stated that reactions involve rearrangement, not creation or destruction, of atoms.

Step 3: Conclusion
The incorrect postulates are:

(B), (D) only