Silicon

Silicon does not react with most acids, under normal conditions. It is dissolved by hydrofluoric acid, HF, most likely due to the complex formation of [SiF₆]²⁻, as the driving force.

Si(s) + 6 HF(aq) [SiF₆]²⁻(aq) + 2H⁺(aq) + 2 H₂(g)

Silicon is passivated by a thin layer of SiO₂ on the surface, and does not otherwise react with air under normal conditions.

If heated above 900 °C, silicon reacts with the oxygen, O₂, forming SiO₂:

Si(s) + O₂(g) SiO₂(s)


If heated above 1400 °C, silicon reacts with the nitrogen, N₂, forming the silicon nitrides SiN and Si₃N₄:

2 Si(s) + N₂(g) 2 SiN(s)
3 Si(s) + 2 N₂(g) Si₃N₄(s)

Silicon reacts with hot alkali solutions, forming silicate ions, SiO₃²⁻ [5]:

Si(s) + 2 OH⁻(aq) SiO₃²⁻(aq) + 2 H₂(g)

Silicon reacts halogens, forming the corresponding Si(IV) halides.

Si(s) + 2 F₂(g) SiF₄(g) [5]
Si(s) + 2 Cl₂(g) SiCl₄(l) [5]
Si(s) + 2 Br₂(g) SiBr₄(l)
Si(s) + 2 I₂(g) SiI₄(s)

Silicon does not react with water, even as steam, under normal conditions.

Method 4500-Si G Inductively Coupled Plasma Method [1]. A portion of the sample is digested in a combination of acids. The digest is aspirated into an 8,000 K argon plasma where resulting light emission is quantified for 30 elements simultaneously.

Method limit of detection in water = 0.05 mg/L