Atomic Number | 2 |
---|---|
Atomic Weight | 4.002602 |
Mass Number | 4 |
Group | 18 |
---|---|
Period | 1 |
Block | s |
Protons | 2 p+ |
---|---|
Neutrons | 2 n0 |
Electrons | 2 e- |
Atomic Radius | 120 pm
|
---|---|
Molar Volume | 31.8 cm³/mol
|
Covalent Radius | 46 pm
|
Metallic Radius | |
Ionic Radius | |
Crystal Radius | |
Van der Waals Radius |
140 pm
|
Density | 0.000164 g/cm³
|
Energy | |
Proton Affinity | 177.8 kJ/mol
|
Electron Affinity | -19.7 eV/particle
|
Ionization Energy | 24.587387936 eV/particle
|
Heat of Vaporization | 0.08 kJ/mol
|
Heat of Fusion | |
Heat of Formation | |
Electrons | |
Electron Shells | 2 |
Valence Electrons | 2 |
Electron Configuration | 1s2 |
Oxidation States | |
Electronegativity | |
Electrophilicity | 0.0674191963846371 eV/particle
|
Phases | |
Phase | Gas |
Gas Phase | Monoatomic |
Boiling Point | 4.222 K
|
Melting Point | |
Critical Pressure | 0.22746 MPa
|
Critical Temperature | 5.195 K
|
Triple Point | |
Visual | |
Color | Colorless
|
Appearance | colorless gas, exhibiting a red-orange glow when placed in a high-voltage electric field |
Refractive Index | 1.000035
|
Thermodynamic Properties | |
Thermal Conductivity | 0.152 W/(m K)
|
Thermal Expansion | |
Molar Heat Capacity | 20.786 J/(mol K)
|
Specific Heat Capacity | 5.193 J/(g⋅K)
|
Heat Capacity Ratio (Adiabatic Index) | 5/3 |
Electrical Properties | |
Type | |
Electrical Conductivity | |
Electrical Resistivity | |
Superconducting Point | |
Magnetism | |
Type | diamagnetic |
Magnetic Susceptibility (Mass) | -0.0000000059 m³/Kg
|
Magnetic Susceptibility (Molar) | -0.0000000000236 m³/mol
|
Magnetic Susceptibility (Volume) | -0.00000000105
|
Magnetic Ordering | |
Curie Point | |
Neel Point | |
Structure | |
Crystal Structure | Face Centered Cubic (HEX) |
Lattice Constant | 3.57 Å
|
Lattice Angles | π/2, π/2, π/2 |
Mechanical Properties | |
Hardness | |
Bulk Modulus | |
Shear Modulus | |
Young Modulus | |
Poisson Ratio | |
Speed of Sound | 970 m/s
|
Classification | |
Category | Noble gases, Noble gases |
CAS Group | VIII |
IUPAC Group | VIIIA |
Glawe Number | 1 |
Mendeleev Number | 112 |
Pettifor Number | 1 |
Geochemical Class | volatile |
Goldschmidt Class | atmophile |
Other | |
Gas Basicity | 148.5 kJ/mol
|
Dipole Polarizability | |
C6 Dispersion Coefficient | 1.42 a₀
|
Allotropes | |
Neutron Cross Section | 0.007
|
Neutron Mass Absorption | 0.00001
|
Quantum Numbers | 1S0 |
Space Group | 225 (Fm_3m) |
Stable Isotopes | 2 |
---|---|
Unstable Isotopes | 6 |
Radioactive Isotopes | 6 |
Abundance | 0.0002 ± 0.0002
|
---|---|
Relative Atomic Mass | |
Mass Number | 3 |
G-Factor | -4.25525062 ± 0.00000006
|
Half Life | |
Spin | 1/2 |
Quadrupole Moment | 0
|
Discovery Year | 1934 |
Parity | + |
Abundance | 99.9998 ± 0.0002
|
---|---|
Relative Atomic Mass | |
Mass Number | 4 |
G-Factor | 0
|
Half Life | |
Spin | 0 |
Quadrupole Moment | 0
|
Discovery Year | 1908 |
Parity | + |
Abundance | Radioactive ☢️ |
---|---|
Relative Atomic Mass | |
Mass Number | 5 |
G-Factor | |
Half Life | 602 ± 22 ys
|
Spin | 3/2 |
Quadrupole Moment | |
Discovery Year | 1937 |
Parity | - |
Decay Mode | Intensity |
---|---|
n (neutron emission) | 100% |
Abundance | Radioactive ☢️ |
---|---|
Relative Atomic Mass | |
Mass Number | 6 |
G-Factor | 0
|
Half Life | 806.92 ± 0.24 ms
|
Spin | 0 |
Quadrupole Moment | 0
|
Discovery Year | 1936 |
Parity | + |
Decay Mode | Intensity |
---|---|
β− (β− decay) | 100% |
β− d (β−-delayed deuteron emission) | 0.000278% |
Abundance | Radioactive ☢️ |
---|---|
Relative Atomic Mass | |
Mass Number | 7 |
G-Factor | |
Half Life | 2.51 ± 0.07 zs
|
Spin | 3/2 |
Quadrupole Moment | |
Discovery Year | 1967 |
Parity |
Decay Mode | Intensity |
---|---|
n (neutron emission) | 100% |
Abundance | Radioactive ☢️ |
---|---|
Relative Atomic Mass | |
Mass Number | 8 |
G-Factor | 0
|
Half Life | 119.5 ± 1.5 ms
|
Spin | 0 |
Quadrupole Moment | 0
|
Discovery Year | 1965 |
Parity | + |
Decay Mode | Intensity |
---|---|
β− (β− decay) | 100% |
β− n (β−-delayed neutron emission) | 16% |
β− t (β−-delayed triton emission) | 0.9% |
Abundance | Radioactive ☢️ |
---|---|
Relative Atomic Mass | |
Mass Number | 9 |
G-Factor | |
Half Life | 2.5 ± 2.3 zs
|
Spin | 1/2 |
Quadrupole Moment | 0
|
Discovery Year | 1987 |
Parity |
Decay Mode | Intensity |
---|---|
n (neutron emission) | 100% |
Abundance | Radioactive ☢️ |
---|---|
Relative Atomic Mass | |
Mass Number | 10 |
G-Factor | 0
|
Half Life | 260 ± 40 ys
|
Spin | 0 |
Quadrupole Moment | 0
|
Discovery Year | 1994 |
Parity | + |
Decay Mode | Intensity |
---|---|
2n (2-neutron emission) | 100% |
French astronomer Jules Janssen obtained the first evidence of helium during the solar eclipse of 1868. Norman Lockyer and Edward Frankland suggested the name helium for the new element. In 1895, Sir William Ramsay discovered helium in the uranium mineral cleveite. It was independently discovered in cleveite by Per Teodor Cleve and Abraham Langlet. From the Greek word helios, the sun
Discoverers | Sir William Ramsey, Nils Langet, P.T.Cleve |
---|---|
Discovery Location | Scotland/Sweden |
Discovery Year | 1895 |
Etymology (Name Origin) | Greek: hêlios (sun). |
Pronunciation | HEE-li-em (English) |
Found in natural gas deposits & in the air (5 parts per billion) Constantly lost to space; replenished by radioactive decay (alpha particles).
Abundance | |
---|---|
Abundance in Earth's crust | 0.008 mg/kg
|
Abundance in Oceans | 0.000007 mg/L
|
Abundance in Human Body | |
Abundance in Meteor | |
Abundance in Sun | 23 %
|
Abundance in Universe | 23 %
|
1 | s | 0.3125 |