1. The Octet Rule

2. Noble Gases: the happiest elements • 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.

3. Octet Rule 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 Electrons He 2 Ne 8 Ar8 Kr8 In order to achieve an octet, elements will form ions.

4. 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+

5. Formation of a Sodium Ion, Na+ Sodium achieves an octet by losing its one valence electron.

6. Charge of Sodium Ion, Na+ With the loss of its valence electron, a sodium ion has a 1+ charge. Sodium atom Sodium ion 11p+ 11p+ 11e–10e– 0 1 +

7. Formation of Magnesium Ion, Mg2+ Magnesium achieves an octet by losing its two valence electrons.

8. Charge of Magnesium Ion, Mg2+ With the loss of two valence electrons magnesium forms a positive ion with a 2+ charge. Mg atom Mg2+ ion 12p+ 12p+ 12e–10e– 0 2+

9. 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

10. Formation of a Chloride Ion, Cl– Chlorine achieves an octet by adding an electron to its valence electrons.

11. 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–