Find the oxidation number of the element in bold in the following speices
`(i) SiH_(4), BH_(3),BF_(3),S_(2)O_(3)^(2-),BrO_(4)^(-) "and" HPO_(4)^(2-)
(ii) PbSO_(4),U_(2)O_(7)^(2-),CrO_(4)^(2-), K_(2)MnO_(4)`

Explanation

(i)`Si=-4 in SiH_(4), B=-3 in BH_(3) , B=+3 in BF_(3),S=+2 in S_(2)O_(2)^(2-),Br=+7 in Br_(4)^(-) nd P=+5 in HPO_(4)^(2-)`
`(ii) S=+6 in Pb SO_(4), U=+5 in U_(2)O_(7)^(4-), B=+3 in B_(4)O_(7)^(2-)Cr =+ CrO_(4)^(2-)` and Mn=+6 in `K_(2)MnO_(4)`