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Silicate Minerals :white_circle: - Coggle Diagram
Silicate Minerals
:white_circle:
Silicate Minerals
Atomic structure influences properties
Silicon
Cations
Positive charge of 4
Oxygen
Anions
Negative charge of 2
Silicon and oxygen are attracted to each other
Share electrons
Form covalent bonds
Atom radius of silicon is smaller than oxygen
Silicon can be surrounded by 4 oxygen
Form tetrahedron
Charge of 4-
one electron from each oxygen is shared
leaves 4 electrons to bond with other cations
Quartz
Bond with silicon
Structures can be arranged in different ways
Cations fill the spaces in between
Sodium
Potassium
Calcium
Magnesium
Irom
Aluminium
Single Tetrahedra
:one:
Simplest silicate structures
Single tetrahedra bonded to cations
1:4
Olivine
Two Mg or Fe or one of each
Balance the charge of 4-
Cations
Have similar atomic radii
Substitute for one another
Solid Solution
Olivine forms at high temps
Earlier than minerals that have more complex structures
Chains
:chains:
Silicate tetrahedra shares two of its oxygen with an adjacent
Bridging oxygen
1:3
Each chain of 2 tetrahedra has a 2- charge
Balanced by Mg or Fe
Pyroxenes
Weaker bonds result in two cleavage directions
Roughly at 90 degrees
Double Chains
:chains::chains:
Two single chains are combined to form double chains
Alternate tetrahedra in two parallel chains are linked
4:11
Each double chain has a 6- charge
Holes between accommodate OH ions
Resulting in amphiboles
Less compact than sigle chains
Reduces density
Mg, Fe, Al link the chains
Sheets
:bed:
Form when each tetrahedron shares three of it oxygen atoms with adjacent tetrahedra
2:5
Spaces accommodate OH ions
Account for low densities
Each sheet as a charge of 4-
Weak K-O bonds in micas
Explains good cleavage
Frameworks
:frame_with_picture:
Form when all four oxygens are shared
1:2
No charge
Quartz
Strong Si-O bonds
Feldspars
Weaker bonds between the oxygen and cations
Cleavage in 2 directions
Polymerisation
:fishing_pole_and_fish:
Small molecules can join up to make larger ones
Link to form polymers by oxygen sharing
Resistence to flow is affected in liquids where polymers are formed
Resistance to flow is affected in liquids where polymers are formed