He

Helium

Identification

CAS Number: 7440-59-7

Discovery Year: 1895

Discoverer: Sir William Ramsey, Nils Langet, P.T.Cleve

Discovery Location: Scotland/Sweden

Properties

Atomic Mass: 4.002602 →Density: 0.000164 g/cm³ →

Crust Abundance: 0.008 mg/kg

Crystal Structure: HEX

Atomic Dimensions

Atomic Radius: 120 pm →

Atomic Radius (Rahm): 134 pm

Covalent Radius: 28.000000000000004 pm →

Van der Waals Radius: 140 pm

Atomic Volume: 31.8 cm³/mol

Lattice Constant: 3.57 Å

Thermodynamics

Melting Point: 0.95 K →Boiling Point: 4.216 K →Specific Heat: 5.188 J/(g·K) →Thermal Conductivity: 0.152 W/(m·K) →Heat of Vaporization: 0.08 kJ/mol →

Electronic Structure

Electron Config: 1s2

Block: s

Period: 1 →Group: 18 →Electron Affinity: -19.7 eV →

Oxidation States: 0

Abundance & Geochemistry

Crust Abundance: 0.008 mg/kg

Sea Abundance: 0.000007000000000000001 mg/L

Geochemical Class: volatile

Goldschmidt Class: atmophile

About

Helium is a colorless, odorless, tasteless, non-toxic, inert noble gas. It is the second lightest element and is used in balloons, diving equipment, and cooling systems.

Isotopes

He-4 4 100.00%

He-3 3 2.00e-4%