Ussama Rasool Qadri
Ussama Rasool Qadri answered question
Helium Atomic Number: 2 Symbol: He Atomic Weight: 4.00260 Discovery: Janssen, 1868, some sources say Sir William Ramsey, Nils Langet, P.T. Cleve 1895 Electron Configuration: 1s2 Word Origin: Greek: Helios, sun. Helium was first detected as a new spectral line during a solar eclipse. Isotopes: 7 isotopes of helium are known. Properties: Helium is a … Read more