Electronic structure: 288 rule

In this lesson, we will learn:
• A method to determine electronic structure in atoms.
• The reason electronic structure is important to understanding chemical elements.
• How to predict the number of outer shell electrons in elements.

Notes:

• Electrons in atoms exist outside the nucleus in energy levels sometimes known as shells. The number of electrons in an atom's outer electron shell is called the electron shell configuration.

• The reactivity of an element is strongly linked to the number of outer shell electrons an atom of the element has. Elements react in ways to obtain a full outer shell, whether by sharing, losing or gaining electrons (see our videos on bonding and types of compounds).

• The 1st, 2nd, and 3rd shells can hold 2, 8 and 8 electrons respectively. Once a shell is filled up, any further electrons must fill in a new higher level shell.

• The number of outer shell electrons is a defining factor of how the periodic table is laid out: elements in the same group have the same outer shell electron configuration.