For a compound LiAl(SiO_(3))_(2),What is thecharge on the SiO_(3) unit. What is the arrangement of oxygenatoms aroundthe siliconatom ?

For a compound LiAl(SiO_(3))_(2),What is thecharge on the SiO_(3) unit

1.	For a compound LiAl(SiO_(3))_(2),What is thecharge on the SiO_(3) unit. What is the arrangement of oxygenatoms aroundthe siliconatom ?
Answer» Solution :Since lithiumhas one unit `+ve`chargeand aluminium has THREE units+ve charge, therefore, TOTAL+ve chargeon cations is 4. Sincethe mineral`LiAl(SiO_(3))_(2)` is electricity neutral, therefore, total -ve chargeon TWO `SiO_(3)` unitsis `-4`or each `SiO_(3)` unit mustcarry two units-ve chargeand must berepresentedas `SiO_(3)^(2-)`. We know that all silicates consist of `SiO_(4)^(4-)`tetrahedra. But from theformula of thegiven silicate, it appears that there areonly 3oxygenper SILICON atom. This canbe explainedif two of theoxygenatoms ofeach `SiO_(4)^(4-)`unitshare with each othergiving a simple chainstructure for the silicate, `LiAl(SiO_(3))_(2)` as shown below: