What is the lightest element known to science?

Hydrogen is the lightest element known to science because it has the smallest atomic number, which is one. This means it consists of only one proton and typically one electron. In the periodic table, hydrogen is located at the topmost position, indicating that it is the simplest and least massive element. Its low atomic weight makes it less dense than all other elements, contributing to its classification as the lightest.

Other elements, such as helium, oxygen, and lithium, have higher atomic numbers and consist of more protons, neutrons, and electrons, resulting in greater atomic masses. For instance, helium has two protons, oxygen has eight, and lithium has three. Thus, while these elements possess various properties and uses, they are not as light as hydrogen, thereby affirming hydrogen's status as the lightest element in the universe.