1.

Silicon forms very strong bonds to oxygen and fluorine (particularly to oxygen) - this provides a driving force for much of silicon's chemistry.

2.

Silicon is more electropositive than carbon, so when bonded to carbon it often represents an attractive site for nucleophilic attack (i.e. it has δ⁺) - particularly if a halogen is attached.

3.

The mechanism for nucleophilic substitution is very similar to that for S_N2, except that the 5-coordinate transition state in the latter is replaced by a 5-coordinate intermediate in the former. For example;

4.i.

Carbocations β to silicon are stabilised by it.

4.ii.

Carbanions α to silicon are stabilised by it.

5.

Silylcarbinols (see the example below for what a silylcarbinol is) can undergo 1,2-rearrangements if treated with a catalytic amount of base or active metal (e.g. Na/K alloy). The following example shows the mechanism of such rearrangements;