Layer Silicates

Question 1

2-Layer Structures

Answer 1

Dioctahedral or trioctahedral

Question 2

Kaolinite

Answer 2

Al4Si4O10(OH)8

Dioctahedral 2-later silicate

Question 3

Chrysotile

Answer 3

Mg6Si4O10(OH)8

Trioctahedral 2-Layer silicate

Question 4

Muscovite

Answer 4

KAl2(AlS3)O10(OH)2

3-later silicate

Question 5

Gibbsite

Formula, structure, coordination, bond length

Answer 5

Al2(OH)3
Layer silicate (H/O/Al,Al,vac./O/H)
Al: octahedral coord. (6)
O: deformed triangular (2H, 1Al)
Al-O: 1.9 A   [rAl = 0.54 A; rO = 1.35 A;
O-H: 1.0 A.    Then Al-O bond = 1.89 A]
[rH = 0.35 A]

Question 6

Brucite

Formula, structure, coordination, bond length

Answer 6

Mg2(OH)3
Trioctahedral Layer silicate: H/O/Mg/O/H
Mg: octahedral (6)
O: deformed tetrahedral (4)
Mg-O bond = 1.35+0.7=2.05 A ~=2 A
O-H bond = 1 A

Question 7

For every ____ Mg atoms in Brucite, there are _____ Al atoms and ______ vacancies in Gibbsite.

Answer 7

3 Mg = 2 Al + [ ]

Question 8

There are two types of layers present in silicates:

Answer 8

Octahedral layers

&

Tetrahedral layers

Question 9

Octahedral layers have _____-sharing octahedra

Answer 9

Edge

Question 10

Tetrahedra layers have _______-sharing tetrahedra.

Ex. SiO4 (isolated tetrahedra)

Answer 10

Corner