Хелиум

2
He
Група
18
Периода
1
блок
s
Protons
Electrons
Neutrons
2
2
2
Општи Својства
Атомски број
2
Атомска тежина
4,002602
Mass Number
4
Category
Благородни гасови
Color
Colorless
Radioactive
Не
From the Greek word helios, the sun
Кристална структура
Face Centered Cubic
History
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.
Electrons per shell
2
Електронска конфигурација
1s2
He
Unlike any other element, helium will remain liquid down to absolute zero at normal pressures
Физички Својства
Фаза
Gas
Густина
0,0001785 g/cm3
Точка на топење
0,95 K | -272,2 °C | -457,96 °F
Точка на вриење
4,22 K | -268,93 °C | -452,07 °F
Топлина на топење
0,02 kJ/mol
Топлина на испарување
0,083 kJ/mol
Specific Heat Capacity
5,193 J/g·K
Abundance in Earth's crust
5,5×10-7%
Abundance in Universe
23%
Vial
Кредити на слика: Images-of-elements
Vial of glowing ultrapure helium
CAS Number
7440-59-7
PubChem CID Number
23987
Атомски Својства
Атомски полупречник
31 pm
Ковалентен полупречник
28 pm
Електронегативност
-
Ionization Potential
24,5874 eV
Atomic Volume
27,2 cm3/mol
Thermal Conductivity
0,00152 W/cm·K
Oxidation States
0
Applications
Helium is used as a protective gas in growing silicon and germanium crystals, in titanium and zirconium production, and in gas chromatography.

Helium at low temperatures is used in cryogenics.

Helium is used for filling balloons and for pressurizing liquid fuel rockets.

Helium is used as a shielding gas in arc welding processes.
Helium is not known to be toxic
Isotopes
Stable Isotopes
3He, 4He
Unstable Isotopes
5He, 6He, 7He, 8He, 9He, 10He