Silicon

Silicon is atom number 14 — every Silicon atom has exactly 14 protons in its center, and that number is what makes it Silicon and nothing else. Its symbol is Si. At room temperature it is a solid.

Silicon is a chemical element with symbol Si and atomic number 14. It is a tetravalent metalloid, more reactive than germanium, the metalloid directly below it in the table. Controversy about silicon's character dates to its discovery.

Summary from the source dataset, derived from Wikipedia (CC BY-SA 3.0) · original article

Silicon sits in period 3, group 14 of the p-block. Its 14 electrons fill shells of 2, 8, 4 — written as [Ne] 3s2 3p2. Its electronegativity is 1.9 on the Pauling scale, and pulling the first electron off takes 786.5 kJ/mol. The outermost shell holds 4 electrons — the ones that do all the chemistry.

Full configuration: 1s2 2s2 2p6 3s2 3p2
Ionization energies (kJ/mol): 786.5, 1577.1, 3231.6, 4355.5, 16091, 19805, 23780, 29287 … (14 published)
Electron affinity: 134.0684 kJ/mol · Electronegativity (Pauling): 1.9
Density: 2.329 g/cm³ · melts 1687 K · boils 3538 K

Values exactly as published — see where the data comes from.