Hílíọ̀mù, 2 He Hílíọ̀mù Pípè / ˈ h iː l i ə m / (HEE -lee-əm ) Ìhànsójú ẹ̀fúùfù aláìláwọ̀, yíò tan àwọ̀ ọsàn-pupa tó bá wà nínú pápá ìtanna ìtiná gíga Ìwúwo átọ̀mù A r, std (He) 4.0026 02(2) [ 1] Hílíọ̀mù ní orí tábìlì àyè
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 Color lines in a spectral range Spectral lines of hílíọ̀mùOther 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 [ 2] 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
Atmospheric value, abundance may differ elsewhere.
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References
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↑ Meija, Juris; Coplen, Tyler B.; Berglund, Michael; Brand, Willi A.; De Bièvre, Paul; Gröning, Manfred; Holden, Norman E.; Irrgeher, Johanna et al. (2016). "Atomic weights of the elements 2013 (IUPAC Technical Report)". Pure and Applied Chemistry 88 (3): 265–91. doi :10.1515/pac-2015-0305 .
↑ Magnetic susceptibility of the elements and inorganic compounds , in Handbook of Chemistry and Physics 81st edition, CRC press.