6.3 : Silicon Compounds

What is Silicons ?

•  Silicon is a non-metallic element •  The second most plentiful element in the Earth’s

crust after oxygen •  Solid element with a melting point of 1410°C •  When heated strongly in the air, it forms silicon

dioxide (silica) •  Silicon usually combines with other elements to

form silica and silicates •  Silica & silicates form about 90% of the Earth’s

crust

Silicon    +    Oxygen                  heat   Silicon  

dioxide  Prepared  by  Ms  Sue  Soh  

What are SILICA and SILICATES ?

•  Silica is silicon dioxide (compound of silicon & oxygen)

•  Examples : Pure sand, quartz, flint

6.3 : Silicon Compounds

Prepared  by  Ms  Sue  Soh  

What are SILICA and SILICATES ?

•  Silicate : compound of silicon which consists metal, silicon and oxygen

•  Example : Copper silicate contains COPPER, SILICON and OXYGEN

•  Most minerals are silicates and their colours depends on the metal in it

6.3 : Silicon Compounds

Copper  silicate  

Iron  silicate  

Nickel  silicate  

Manganese  silicate  

Prepared  by  Ms  Sue  Soh  

•  Many precious stones used for decoration are silicates

•  Examples : Ruby, Topaz, Jade

•  Other common silicates are : –  Clay (aluminium

silicate) –  Mica (potassium

aluminium silicate) –  Feldspar

(potassium aluminium silicate + sodium aluminium silicate)

–  Asbestos (calcium silicate + magnesium silicate)

6.3 : Silicon Compounds Ruby  

Jade  

Topaz  

What are SILICA and SILICATES ?

Prepared  by  Ms  Sue  Soh  

Properties of Silicon Compounds

•  Silicon compounds are very stable –  Do not dissolve in water (except sodium silicate) –  Do not react with acids –  Do not decompose on heating

•  Silicon compounds are plentiful (sand) they are very stable substances

•  Silica is acidic & reacts with alkalis to form silicates

•  Silicates do not react with alkalis

6.3 : Silicon Compounds

 Silicon    +  Alkali                  heat  

Silicate  +  Water  

Prepared  by  Ms  Sue  Soh  

Uses of Silicon Compounds •  A chemical garden of silicate “plants” can be

grown by adding crystals of different coloured salts into a sodium silicate solution

•  The plants formed are insoluble silicates

6.3 : Silicon Compounds

Prepared  by  Ms  Sue  Soh