Calculate the oxidation number of the underlined elements in each of the following species.
(i) `NaH_(2)ul(P)O_(4)`
(ii) `NaH ul(S)O_(4)`
(iii) `H underset(4-2)(P) O_(7)`
(iv) `K_(2) ul(Mn)O_(4)`

Explanation

(i) `NaH_(2)ul(P)O_(4)`
Let the oxidation number of P be x. Write the oxidation number of each atom above its symbol.
`{:(+1,,+1,,x,,-2),(Na,,H_(2),,P,,O_(4)),((+1),+,(1xx2),+,x,+,(-2 xx 4)=0):}`
1 + 2 + x - 8 = 0
3 + x - 8 = 0
x = 5
`therefore` oxidation number of P in `NaH_(2)PO_(4)` is +5.
(ii) `NaH ul(S)O_(4)`
Let the oxidation number of S be x. Write the oxidation number of each atom above its symbol.
`{:(+1,,+1,,x,,-2),(Na,,H,,S,,O_(4)),((+1),+,(+1),+,x,+,(-2 xx 4)=0):}`
2 + x - 8 = 0
x = 6
`therefore` oxidation number of S in `NaH ul(S)O_(4)` is +6.
(iii) `H underset(4-2)(P)O_(7)`
Let the oxidation number of P be x. Write the oxidation number of each atom above its symbol.
`{:(+1,,x,,-2),(H_(4),,P_(2),,O_(7)),((+1xx4),+,(x xx 2),+,(-2 xx 7) = 0):}`
4 + 2x - 14 = 0
2x = 10
x = 5
`therefore` oxidation number of P in `H_(4)P_(2)O_(7)` is +5.
(iv) `K_(2) ul(Mn) O_(4)`
Let the oxidation number of Mn be x. Write the oxidation number of each atom above its symbol.
`{:(+1,,x,,-2),(K_(2),,Mn,,O_(4)),((+1xx2),+,x,+,(-2 xx 4) = 0):}`
2 + x - 8 = 0
x = 6
`therefore` oxidation number of Mn in `K_(2)MnO_(4)` is +6.