Illites contain interlayer cations of:

Correct option is B

The correct answer is (b) K. Illite is a type of clay mineral that contains potassium (K) as an interlayer cation. The structure of illite is similar to muscovite mica, and potassium ions help bind the layers together.
Structure of Illite:
· Composition:
· General formula: (K, H)Al₂(Si, Al)₄O₁₀(OH)₂.
· Potassium ions (K⁺) occupy the interlayer spaces between the silicate sheets.
Breakdown of Other Options:
1. (a) Na (Sodium):
· Found in clay minerals like smectite and montmorillonite, but not in illite.
2. (c) Mg (Magnesium):
· Found in minerals like chlorite and smectite, but not a primary interlayer cation in illite.
3. (d) Fe (Iron):
· Present in some clay minerals as a structural component but not as an interlayer cation in illite.
Information Booster 1. Illite Characteristics:
· Non-expanding clay mineral.
· Commonly found in sedimentary rocks and soils.
· Formed from the weathering of feldspar and mica.
2. Uses of Illite:
· In ceramics, drilling muds, and as a component in soil.
3. Interlayer Cations in Clays:
· Illite: Potassium (K).
· Montmorillonite: Sodium (Na) or Calcium (Ca).
· Chlorite: Magnesium (Mg) or Iron (Fe).
Additional Knowledge · Clay Minerals:
· Kaolinite: Non-expanding clay, used in ceramics.
· Smectite: Expanding clay, high water absorption.
· Illite: Non-expanding, potassium-rich clay.