Hílíọ̀mù

Hílíọ̀mù, ₂He

Hílíọ̀mù
Pípè	/ˈhiːliəm/ ​(HEE-lee-əm)
Ìhànsójú	ẹ̀fúùfù aláìláwọ̀, yíò tan àwọ̀ ọsàn-pupa tó bá wà nínú pápá ìtanna ìtiná gíga
Ìwúwo átọ̀mù Ar, std(He)	4.002602(2)
Hílíọ̀mù ní orí tábìlì àyè
Hydrogen Helium Lithium Beryllium Boron Carbon Nitrogen Oxygen Fluorine Neon Sodium Magnesium Aluminium Silicon Phosphorus Sulfur Chlorine Argon Potassium Calcium Scandium Titanium Vanadium Chromium Manganese Iron Cobalt Nickel Copper Zinc Gallium Germanium Arsenic Selenium Bromine Krypton Rubidium Strontium Yttrium Zirconium Niobium Molybdenum Technetium Ruthenium Rhodium Palladium Silver Cadmium Indium Tin Antimony Tellurium Iodine Xenon Caesium Barium Lanthanum Cerium Praseodymium Neodymium Promethium Samarium Europium Gadolinium Terbium Dysprosium Holmium Erbium Thulium Ytterbium Lutetium Hafnium Tantalum Tungsten Rhenium Osmium Iridium Platinum Gold Mercury (element) Thallium Lead Bismuth Polonium Astatine Radon Francium Radium Actinium Thorium Protactinium Uranium Neptunium Plutonium Americium Curium Berkelium Californium Einsteinium Fermium Mendelevium Nobelium Lawrencium Rutherfordium Dubnium Seaborgium Bohrium Hassium Meitnerium Darmstadtium Roentgenium Copernicium Nihonium Flerovium Moscovium Livermorium Tennessine Oganesson - ↑ He ↓ Ne háídrójìn ← hílíọ̀mù → lítíọ̀mù
Nọ́mbà átọ̀mù (Z)	2
Ẹgbẹ́	group 18 (noble gases)
Àyè	àyè 1
Àdìpọ̀	Àdìpọ̀-s
Ẹ̀ka ẹ́límẹ́ntì	Ẹ̀fúùfù abíire
Ìtò ẹ̀lẹ́ktrọ́nù	1s2
Iye ẹ̀lẹ́ktrọ́nù lórí ìpele kọ̀ọ̀kan	2
Àwọn ohun ìní ara
Ìfarahàn at STP	ẹ̀fúùfù
Ìgbà ìyọ́	(at 2.5 MPa) 0.95 K ​(−272.20 °C, ​−457.96 °F)
Ígbà ìhó	4.22 K ​(−268.93 °C, ​−452.07 °F)
Kíki (at STP)	0.1786 g/L
when liquid (at m.p.)	0.145 g/cm3
when liquid (at b.p.)	0.125 g/cm3
Critical point	5.19 K, 0.227 MPa
Heat of fusion	0.0138 kJ/mol
Heat of	0.0829 kJ/mol
Molar heat capacity	5R/2 = 20.786 J/(mol·K)
pressure (defined by ITS-90) P (Pa) 1 10 100 1 k 10 k 100 k at T (K)     1.23 1.67 2.48 4.21
Atomic properties
Oxidation states	0
Electronegativity	Pauling scale: no data
Covalent radius	28 pm
Van der Waals radius	140 pm
Spectral lines of hílíọ̀mù
Other properties
Natural occurrence	primordial
Crystal structure	​hexagonal close-packed (hcp)
Speed of sound	972 m/s
Thermal conductivity	0.1513 W/(m·K)
Magnetic ordering	diamagnetic
CAS Number	7440-59-7
History
Discovery	Pierre Janssen, Norman Lockyer (1868)
First isolation	William Ramsay, Per Teodor Cleve, Abraham Langlet (1895)
Main isotopes of hílíọ̀mù
Iso­tope Abun­dance Half-life (t1/2) Decay mode Pro­duct 3He 0.000137%* 3He is stable with 1 neutron 4He 99.999863%* 4He is stable with 2 neutrons
Atmospheric value, abundance may differ elsewhere.

Hílíọ̀mù, Hélíọ̀m, tabi Helium (pípè /ˈhiːliəmu/, HEE-lee-əm) ni ẹ́límẹ̀ntì kẹ́míkà tó ní nọ́mbà átọ́mù 2 àti iwuwo atomu to je 4.002602, àmì ìdámọ̀ rẹ̀ ni He. O je efuufu oniatomukan, alaigbera, aláìláwọ̀, alailoorun, alainitowo, ati alailewu to siwaju ẹgbẹ́ ẹ̀fúùfù abíire ninu tabili asiko. Awon ojuami ìhó àti ìyọ́ rẹ̀ je awon ti won kerejulo larin awon ẹ́límẹ̀ntì, o si wa pere gege bi efuufu ayafi nigba to ba wa nipo lounloun. Leyin hydrogen, ohun ni elimenti keji to pojulo ni agbalaaye, o si je bi 24% gbogbo akojo elimenti ninu galaksi wa.