Question

List all possible unit formulas (chemical formulas) that can be constructed by the formation of binary ionic compounds from the following elements. (Separate substances in a list with a comma.)

Br (Z = 35), Sr (Z = 38), Ca (Z = 20), Ga (Z = 31), O (Z = 8)



Please help! I have no idea what this is asking me to do.

Answer 1

Ionic compounds form between metals and non-metals. You have Sr, Ca, Ga metals and Br and O non-metals.
Examples:
Br and Sr would be SrBr2.
Br and Ga would be GaBr3.
etc. with Br and other metals.
Br and O would be BrO2 but BrO2 isn't that well known AND it isn't ionic so I would include it.
You go through with O and metals but remember to get all of the combinations with Br. I didn't include all of them.

Answer 2

Br ion is -1 in general

Sr ion is +2
Ca ion is +2
Ga ion is +3

O ion is - 2

so Br and O are our negative ions
match them up with the positives (metals)
Sr and Br = SrBr2
Sr and O = SrO

Ca and Br = CaBr2
Ca and O = CaO

Ga and Br = GaBr3
Ga and O = Ga2O3 2*3=6 and 3*2=6