The Periodic Table is a well-organized chart that contains all 118 known elements in the universe. These elements are the ...

Different shells can hold different maximum numbers of electrons. Electrons occupy shells starting with the innermost one. They begin to occupy the next shell when a shell becomes full.

Across a period from left to right, the covalent radius decreases. As you move from left to right across the periodic table, atoms have more electrons in their outer energy level and more protons ...

But how many of these elements do you know? Test your knowledge and compete with other Live Science readers to see who can ...