slap_maxwell said:
I have my chemistry final on Monday- I am having trouble remembering my polyatomic ions. Also going from a chemical eqation (sp) to the written form, but only when there is a roman numeral involved.
Everyone else, especially Piglet - don't even bother reading this!
The Roman numeral refers ONLY to the element with a positive variable oxidation state: e.g. copper(II) cloride is (Cu2+) (Cl-)2
nitric(V) acid is H(+1) (for the acid) N(+5) O(-2)3
The N has +5 because thats what the Roman numeral says, H is always +1 unless it's with a Group 1 metal, and you add oxygens till you get an overall charge of zero.
Going backwards: KMnO4.
K is always +1, O is always -2, so you have got (1 x +1) + (4 x -2) = -7
So, the Mn must be +7 to make it zero overall, i.e.
potassium manganate(VII)
polyatomics:
end in ~ide; single element ion, non-metallic, e.g. chloride Cl-
end in ~ate; one element and oxygen, sulfate = SO4 2-
Learn
carbonate CO3 2-
phosphate PO4 3-
nitrate NO3 -
the rest you have to work out from the numerals.