The incorrect postulates of Dalton's atomic theory are: (A) Atoms of different elements differ in mass. (B) Matter…

🧠 The Father of Atomic Theory John Dalton's 1803 model was groundbreaking but simplified. We need to identify the statements that contradict his original theory, even if we know modern science has updated them (like isotopes).

🗺️ Postulate Evaluation

• (A) Atoms of different elements differ in mass: This is a correct postulate of Dalton's.
• (B) Matter consists of divisible atoms: This is incorrect. Dalton famously stated atoms are indivisible and indestructible.
• (C) Compounds formed in fixed ratio: This is a correct postulate (Law of Definite Proportions).
• (D) All atoms of an element have different mass: This is incorrect. Dalton believed all atoms of the same element were identical in mass and properties. (Modern discovery of isotopes changed this, but here we only care about what Dalton said).
• (E) Chemical reactions involve reorganisation of atoms: This is a correct postulate.

Incorrect Statements are (B) and (D).

⚡ The "Indivisible" Anchor Dalton's entire point was that atoms are like "hard billiard balls" that cannot be split. Any option saying atoms are "divisible" is a dead giveaway for an incorrect postulate.

⚠️ Common Traps Don't apply modern knowledge to a question asking about Dalton's theory. While we today know atoms are divisible (electrons/protons) and can have different masses (isotopes), Dalton didn't. When asked about his theory, stick to what he wrote 200 years ago!

$\boxed{\text{Answer: (b)}}$