Helium is a chemical element in a period table and has symbol He. The atomic number and atomic mass of helium is 2 and 4 respectively. Helium is a gas at room temperature. Helium has two electrons in its orbit. The electronic configuration is 1S2. The shell of helium is completely filled with two electrons and categorized as noble gas. Helium is an inert gas and present in mono-atomic form. Moreover, it is a colorless, odorless and tasteless gas.