Helium is element number 2, with the symbol He. It is the second-lightest element, and after hydrogen it is the most common element in the universe. It was discovered not on Earth but in the Sun.
Atomic number 24.003
HeHeliumヘリウム (heriumu)
Symbol
He
Atomic weight
4.003
Place in the table
Period 1 · Group 18
Atomic weight from the Chemical Society of Japan, “Table of Standard Atomic Weights with Four Significant Figures (2026)”.
Found in the light of the Sun
During the total solar eclipse of 1868, the French astronomer Janssen studied the light of the gas around the Sun and found a bright line that no one had seen before. The English scientist Lockyer concluded that it came from an element nobody knew yet.
It was an element of the Sun, not yet found on Earth, so it was named “helium.” The name and the symbol He come from Helios, the Greek word for the Sun. Helium was confirmed on Earth in 1882.
Made at the beginning of the universe
About three minutes after the universe began, the nuclei of hydrogen and helium formed. The National Astronomical Observatory of Japan explains that before stars formed, helium made up just under a quarter of the mass of all atomic nuclei.
Its atomic weight is 4.003, the second smallest after hydrogen’s 1.008. On the periodic table it sits at the far right of the first row, at the top of Group 18.
Think about it
Q1Why can we tell which elements are in the Sun just by studying its light?
Q2An element was found in the Sun before it was found on Earth. What do you think about that?
Q3If you discovered a new element, what would you name it?
There is no single right answer. Talking it over with someone at home is a good way to learn.
Did you know? — Other elements are named after heavenly bodies too. Tellurium (Te) comes from a word for the Earth, and selenium (Se) from a word for the Moon.