Electron Configuration in Ions - Chemistry Assignment Help

When an element has a noble gas electron configuration, it is surrounded by eight electrons and has the s²p⁶ electron configuration and is extremely stable.  All atoms seek stability, and so they are willing to give up or gain a couple electrons to achieve an electron configuration more like that of a noble gas. Using the electron configuration it is easy to figure out the charge on almost any ion.  

If an atom needs two more electrons to achieve the noble gas electron configuration, then it will try to be a⁺² ion.  If an atom has 1 more electron than the s²p⁶ electron configuration then it will tend to give it up and become a⁺¹ ion.

Example:

What is the electron configuration for the magnesium atom and the magnesium ion?

Magnesium has 12 electrons.

For the magnesium atom the electron configuration is 

1s¹2s²2p⁶ 3s²

At this point we must make a decision.  Ask yourself, would it be easier to add electrons to get the stable s² p⁶ arrangement or would it be easier to lose electrons.  We would have to add 6 electrons to get the noble gas arrangement whereas we soul only have to remove 2 electrons.  It seems like it is easier to take off electrons.   

If we look for the highest energy level that has both s and p orbitals filled and then and trim back to there, we have the electron configuration of the magnesium ion: 

1s¹2s²2p⁶

 So the neutral atom lost 2 electrons.  It now has a⁺² charge.  The ion formed is Mg⁺²