Which noble gas has atomic number 2?

Which noble gas has atomic number 2? The answer is helium. Every helium atom has two protons, and that proton count places it at number 2 on the periodic table.

Helium is the second element and the lightest noble gas. Its electron shell is complete with two electrons, making helium exceptionally unreactive under ordinary conditions. Its symbol is He, and it normally exists as individual atoms rather than molecules such as oxygen’s O₂.

The element was first identified in the Sun’s spectrum in 1868, before scientists found it on Earth. Its name comes from Helios, the Greek Sun god. William Ramsay and other researchers later helped isolate terrestrial helium in the 1890s.

A frequent mistake is confusing atomic number with atomic mass. Helium’s most common isotope has two protons and two neutrons, giving it a mass number of 4. Helium is used in cryogenics, leak detection, welding, and lighter-than-air balloons.