How to know valencies of elements of variable valencies in a compound? Ex - lead oxide Here what should we take valency of lead?

1 Answer
anor277
Jan 17, 2018

You don't know until the formula is specified....

Explanation:

For #"plumbic oxide"#, #PbO_2#, we gots a black powder, and a formal #Pb(+IV)# oxidation state....

For #"plumbous oxide"#, #PbO#, we gots a cream-coloured powder, and a formal #Pb(+II)# oxidation state....

And I like to think of #Pb_3O_4#, #"red lead"#, as a mixed valence oxide, i.e. #Pb_3O_4-=2PbO*PbO_2#, i.e. an adduct of #Pb(II)# and #Pb(IV)# oxides...

And so the formula of the lead oxide must be specified. You are not a mind-reader.

Iron is another metal that has a rich redox chemistry...parallel examples include....

...#Fe_2O_3#, #"ferric oxide"#; #"ferrous oxide"#, #FeO#, and #"magnetite"#, #Fe_3O_4-=FeO*Fe_2O_3#. And there are other iron oxides acessible.....

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