i need some help on understanding why the charges on these ionic compounds are balanced like they are... for example, tin (IV) dichromate is Sn(CrO7)2, but i'm not sure where the +4 of the tin goes, and why there are two dichromates... and mercury (I) nitrate, why are there two mercuries ( Hg2(NO3)2) )?

Question

anonymous · Answer

Dichromate charge is -2
Charge of tin can vary but (IV) represents +4.
All metals (the one in front) is positive,
In order for the charges to balance out the dichromate must be multiplied by 2 in the subscript.

For the second one, Hg usually have a +2.
NO3 (nitrate) has a charge of -1
But this mercury has a +1 charge
So it cannot be $$HgNO _{3}$$
but $$Hg _{2}(NO3)_{2}$$
since it is oxidized.
+2 and -2 would cancel out.