Question

Select the correct sequence of increasing size (thickness) of clay minerals

(A) Montmorillonite

(B) Chlorite

(C) Kaolinite

(D) Illite

Choose the correct answer from the options given below:

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

Hint:

Think about how the crystal structure and bonding of each mineral affects its particle thickness.

Answer 1

The Correct Option is B

Step 1: The thickness of a clay mineral particle depends on its crystal structure. Minerals with an expanding 2:1 lattice form very thin plates, while minerals with a fixed, non-expanding structure form thicker, bulkier particles.

Step 2: Montmorillonite has an expanding 2:1 lattice with weak bonding between layers, so its particles are extremely thin. It has the smallest particle size, and the largest surface area, among common clay minerals.

Step 3: Illite also has a 2:1 structure, but its layers are held together more tightly by potassium ions, which restrict expansion and give it a somewhat larger, thicker particle than montmorillonite.

Step 4: Chlorite has a 2:1:1 structure with an extra brucite-like sheet between the silicate layers, which makes its particles thicker than illite.

Step 5: Kaolinite has a fixed 1:1 structure held together by strong hydrogen bonding between layers, so many layers stack tightly and produce the largest, thickest particles among these four minerals.

So in order of increasing size, the sequence is Montmorillonite, Illite, Chlorite, Kaolinite, that is (A), (D), (B), (C), matching option 2.