మూస:హీలియం మూలకము

హీలియం, ₀₀He

హీలియం
Pronunciation	/ˈhiːliəm/ ​(HEE-lee-əm)
Appearance	colorless gas, exhibiting a red-orange glow when placed in a high-voltage electric field
Standard atomic weight Ar°(He)
	4.002602±0.000002 4.0026±0.0001 (abridged)
హీలియం in the periodic table
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 Ununtrium Flerovium Ununpentium Livermorium Ununseptium Ununoctium - ↑ He ↓ Ne హైడ్రోజన్ ← హీలియం → లిథియం
Group	మూస:Infobox element/symbol-to-group/format
Period	period 1
Block	s-block
Electron configuration	1s2
Electrons per shell	2
Physical properties
Phase at STP	gas
Melting point	(at 2.5 MPa) 0.95 K ​(−272.20 °C, ​−457.96 °F)
Boiling point	4.222 K ​(−268.928 °C, ​−452.070 °F)
Density (at STP)	0.1786 g/L
when liquid (at m.p.)	0.145 g/cm3
when liquid (at b.p.)	0.125 g/cm3
Triple point	2.177 K, ​5.043 kPa
Critical point	5.1953 K, 0.22746 MPa
Heat of fusion	0.0138 kJ/mol
Heat of vaporization	0.0829 kJ/mol
Molar heat capacity	5R/2 = 20.786 J/(mol·K)
Vapor 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 హీలియం
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)
Isotopes of హీలియం

References

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