Silicon (Si) — Atomic Number 14

Silicon is a chemical element with the symbol Si and atomic number 14. It is a hard, dark grey metalloid — the second most abundant element in Earth’s crust (~28%). It is the foundation of modern electronics. The name comes from Latin silex (“flint”).

At a Glance

Structure & Properties

Silicon has a giant covalent structure like diamond — each Si bonded tetrahedrally to 4 others. This gives it a high melting point (~1414 °C). Pure silicon is a semiconductor — poor conductor, but conductivity can be controlled by doping.

Chemical Properties

1. $\text{Si}+{\text{O}}_2\to {\text{SiO}}_2$
2. ${\text{SiO}}_2+2\text{NaOH}\to {\text{Na}}_2{\text{SiO}}_3+{\text{H}}_2\text{O}$ (acidic oxide — reacts with alkali)
3. ${\text{SiO}}_2+2\text{C}\to \text{Si}+2\text{CO}$ (industrial extraction)

Compounds & Uses

• Computer chips and transistors — ultra-pure Si crystals
• Solar panels
• Glass and ceramics

IGCSE Essentials

1. Metalloid — between metals and non-metals
2. Giant covalent structure — high m.p., non-conductive in pure form
3. SiO₂ is acidic (reacts with alkalis, not acids — except HF)
4. 4 valence electrons — like carbon

Sources

• Silicon — Wikipedia
• Silicon — Ptable.com
• Silicon — RSC Periodic Table