Question

Which is not true about the oxidation state of the following elements?
A.Sulphur $+ 6$ to $- 2$
B.Carbon $+ 4$ to $- 4$
C.Chlorine $+ 7$ to $- 1$
D.Nitrogen $+ 3$ to $- 1$

Answer 1

Oxidation number is the charge which an atom or ion of the element contains or appears to have when it is present in combined state with other atoms. It is equal to the group number or it is equal to the number of valence electrons.

Complete step by step answer:
We have to find the incorrect oxidation state for the following compounds-
Sulphur has atomic number $16$ and it is placed in the group $16$ and period $3$.The number of valence electrons is $6$ and we know that to complete the octet the element should have $8$ electrons. So it can have oxidation states from $- 2$ to $+ 6$
Carbon is placed in group $14$ and period $2$. It has atomic number$6$.It has $4$ valence electrons. It can have oxidation states from $+ 4$ to$- 4$.
Chlorine is placed in group $17$ and period $3$. It has atomic number $17$ and the number of valence electrons is $7$. It can have oxidation states from $- 1$ to$+ 7$.
Nitrogen is placed in group $15$ and period$2$. It has atomic number $7$ and the number of valence electrons is $5$. It can have oxidation states from $- 3$ to $+ 5$.
So option D is not true.

The correct answer is option D.

Note:
Oxidation state and valency are two different things so don’t get confused between them.
Valency is the combining capacity of an atom whereas oxidation is the charge on an atom.
Valency is always a whole number while oxidation state can have fractional values
The Valency of an atom cannot be zero but the oxidation state of an element can be zero.