Elements in the same horizontal row are in the same period. The periods are numbered from top to bottom. The period number is the same as the number of occupied electron shells.

Since this atom has a total of eight electrons, it also has eight protons. The atom with eight protons in its nucleus (atomic number 8) is oxygen. Each energy level holds a certain number of electrons ...

Electrons in atoms occupy energy levels, also called electron shells, outside the nucleus. Different shells can hold different maximum numbers of electrons. The electrons in an atom occupy the ...

Students look more deeply into the structure of the atom and play a game to better understand the relationship between protons, neutrons, electrons, and energy levels in atoms and their location in ...

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

Electronegativity, an essential characteristic of all elements in the periodic table, measures an atom's ability to attract electrons towards itself within a chemical bond. This vital theoretical ...

For the last fifty or so years, the periodic table has been incomplete. Elements after uranium on the periodic table have been synthesized for the past few decades, but there were always a few ...