Equal and Unequal Shares

Rgure 2.2.8 Oxygen gets more than its fair share of electrons in water molecules 

Further reading in this area can be done by looking up what is meant by electronegativities . 

One more thing. Metals tend to have only one, two or three electrons in their outermost energy levels. They are not likely, therefore, to be able to 

It can be seen that although the chlorine shells are full, the magnesium outer shell has not got a full octet of electrons, and so this structure is aot the one that is formed in magnesium chloride. 

As a general rule of thumb, if a compoimd contains a metal it will be ionic, and if it contains no metal it will be covalent. 

---