Hydrogen
Definition 1 of 2
Pro Tip 1/3
Science Classes
Hydrogen is often discussed in chemistry and physics as part of the periodic table of elements. In our chemistry class, we learned that hydrogen is the first element on the periodic table.
Pro Tip 2/3
Cosmic Abundance
Hydrogen is the most abundant element in the universe, relevant in space-related contexts. Astronomers estimate that hydrogen makes up about 75% of the universe's elemental mass.
Pro Tip 3/3
Common Compound
Hydrogen is part of many everyday compounds, such as water and organic substances. Every molecule of water has two hydrogen atoms bonded to an oxygen atom.