The Octet Rule

Happy atoms have a full outer energy level of electrons.

They rarely combine with other elements.

Nonreactivity is why they are called noble or inert.

Noble Gases: the happiest elements

An octet is 8 valence electrons is associated with the stability of the noble

gases (does not occur with He; He is stable with 2 valence electrons)

Valence ElectronsHe 2Ne 8 Ar 8

Kr 8In order to achieve an octet, elements

will form ions.

Octet Rule

Metals want to be happy.Metals form cations

by losing their valence electrons resemble the nearest noble gas have fewer electrons than protons

Group 1 metals ion 1+

Group 2 metals ion 2+

Group 3 metals ion 3+

Formation of a Sodium Ion, Na+

Sodium achieves an octet by losing its one valence electron.

Charge of Sodium Ion, Na+

With the loss of its valenceelectron, a sodium ion has a 1+

charge.

Sodium atom Sodium ion 11p+ 11p+

11e– 10e–

0 1 +

Formation of Magnesium Ion, Mg2+

Magnesium achieves an octet by losing its two valence electrons.

Charge of Magnesium Ion, Mg2+

With the loss of two valenceelectrons magnesium forms apositive ion with a 2+ charge.

Mg atom Mg2+ ion 12p+ 12p+

12e– 10e–

0 2+

Nonmetals want to be happy too.

Nonmetals form anions

gain electrons have more electrons than protons form negatively charged ions with

3–, 2–, or 1– charges

Formation of a Chloride Ion, Cl–

Chlorine achieves an octet by adding an electron to its valence electrons.

Charge of a Chloride Ion, Cl–

By gaining one electron, the chloride ion has a –1 charge.

Chlorine atom Chloride ion 17p+ 17p+

17e– 18e–

0 1–