How do you write the formula for barium chloride?

##BaCl_2##

Barium is listed under Group 2A of . Looking at the column, Barium is Ba. The listed in Group 2A have a charge of +2.

So we have Barium as ##Ba^(+2)##

Now let's move to Chloride. Don't bother looking at the table, because it is not listed. Chloride is an ion of Chlorine, which is from Group 7A and we know anything in that column has a charge of -1. So Chlorine has gained an electron and becomes Chloride. Note that this is an anion and has a negative charge. You can see how easy it was to change the name, you just change the suffix to -ide.

So we have Chloride as ##Cl^-##

We're not finished though! The charges do not balance!

To balance it we simply add another Chloride so that you have two negatives balancing the two positives. You'll write it as ##Cl_2##.

Now they balance; you have one barium ##Ba^(+2)## and two chloride ##Cl^-## ##Cl^-##

The final formula is written as ##BaCl_2##.

Hope that helps!