Helium

Helium is atom number 2 — every Helium atom has exactly 2 protons in its center, and that number is what makes it Helium and nothing else. Its symbol is He. At room temperature it is a gas.

Helium is a chemical element with symbol He and atomic number 2. It is a colorless, odorless, tasteless, non-toxic, inert, monatomic gas that heads the noble gas group in the periodic table. Its boiling and melting points are the lowest among all the elements.

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

Helium sits in period 1, group 18 of the s-block. Its 2 electrons fill shells of 2 — written as 1s2. Its electronegativity is — on the Pauling scale, and pulling the first electron off takes 2372.3 kJ/mol. The outermost shell holds 2 electrons — the ones that do all the chemistry.

Full configuration: 1s2
Ionization energies (kJ/mol): 2372.3, 5250.5
Electron affinity: -48 kJ/mol · Electronegativity (Pauling): —
Density: 0.1786 g/L · melts 0.95 K · boils 4.222 K

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