Anirudh Walia is teaching live on Unacademy Plus
Some Important Compounds of Silicon
Silicon dioxide (Si02) Silicon dioxide, commonly known as silica, occurs in various crystallographic forms. For example, Quartz, Cristobalite and thermite are some of the crystalline forms of silica. Structure: Silicon dioxide is a covalent three dimensional network solid. Each silicon atom is covalently bonded in a tetrahedral manner to four oxygen atoms. Each oxygen atom in turn covalently bonded to another silicon atoms as shown below: Si-O-Si-O-Si-O-Si- Si-O-Si-O-Si-O-Si
Properties: (1) In normal form silica is very less reactive. (i) At elevated temperature it does not reacts with halogens, dihydrogen and most of the acids and metals. But it reacts with HF and NaOH Si02+2Na0HNa2Si03+ H20 Si02+ 4HF>SiF+ 2H20 Uses: (1) Quartz is extensively used as a piezoelectric material. (f) Silica gel is used as adsorbent in chromatography (ii) An amorphous form of silica, kieselghur is used in filtration plants.
SILANE (a) Only these two are found. SiH4 & Si2H (Formula Si,H2n2 (b) Higher molecules are not formed. So, Si can't show catenation property Mg2SiH.SO ->MgSO4 SiH Si2Hs (c) SiH4 is more reactive than CH4 due to following reason (G) Si -H and C6 H* C-electronegative than H Si less electronegative than H So bond polarity is reversed when Nu attacks, so it faces repulsion in C but not in Si (ii) Silicon is having vacant d orbital which is not in case of carborn (i Silicon is larger in size compared to C. By which the incoming Nu doesn't face any steric hindrance to attack at Si whereas CH4 is tightly held from all sides.