Silicon is not reactive with :

Nitric, Hydrochloric, and Sulfuric Acids

It is soluble in hydrofluoric acids which creates a gas--Silicon Tetrafluoride



Silicon is reactive with:

Temperatures are a variable in how Silicon reacts.  In normal temperatures Silicon is not reactive with air.  Although, in high temperatures the silicon reacts with oxygen which creates a layer of silica (silicon dioxide).

In very high temperatures Silicon will react with nitrogen and chlorine to form silicon nitride and silicon chloride.