valence+theory

The outermost electrons are the ones responsible for chemical activity, bonding, and physical properties of the elements. These electrons are called //valence electrons//.

The //valence shell// is the total number of electrons in an atom's highest-energy (furthest from nucleus) **s** or **s** and **p** sublevels occupying the same energy level.

The valence shell can be represented using a Lewis diagram. The following table displays the first 20 main group (no transition metals) elements' Lewis diagrams.



The **s** orbital can only hold two electrons; the **p** orbitals can hold up to six electrons. Therefore, the most electrons any element can hold in its valence shell is eight, hence the name given to this property: the //Octet Rule//.

An atom having a full octet of eight valence electrons is satisfied, meaning it will be very chemically stable. Notice that all of the noble gases obey the Octet Rule. This is why these gases are inert - their valence shells are full.

All elements will gain or lose electrons so that they become ions that follow the octet rule.