Helium

2
He
Golongan
18
Periode
1
Blok
s
Proton
Elektron
Neutron
2
2
2
Sifat Umum
Nomor atom
2
Massa atom
4,002602
Nomor massa
4
Kategori
Gas mulia
Warna
Tak berwarna
Radioaktif
Tidak
Dari kata Yunani helios, matahari
Struktur kristal
Kubik Berpusat-muka
Sejarah
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.
Elektron per kulit
2
Konfigurasi elektron
1s2
He
Unlike any other element, helium will remain liquid down to absolute zero at normal pressures
Sifat Fisika
Fase
Gas
Kepadatan
0,0001785 g/cm3
Titik lebur
0,95 K | -272,2 °C | -457,96 °F
Titik didih
4,22 K | -268,93 °C | -452,07 °F
Kalor peleburan
0,02 kJ/mol
Kalor penguapan
0,083 kJ/mol
Kapasitas kalor molar
5,193 J/g·K
Kelimpahan di kerak bumi
5,5×10-7%
Kelimpahan di alam semesta
23%
Vial
Kredit Gambar: Images-of-elements
Vial of glowing ultrapure helium
Nomor CAS
7440-59-7
PubChem CID Number
23987
Sifat Atom
Jari-jari atom
31 pm
Jari-jari kovalen
28 pm
Elektronegativitas
-
Potensi Ionisasi
24,5874 eV
Volume atom
27,2 cm3/mol
Kondusivitas termal
0,00152 W/cm·K
Bilangan oksidasi
0
Aplikasi
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
Isotop
Isotop stabil
3He, 4He
Isotop tidak stabil
5He, 6He, 7He, 8He, 9He, 10He