Question

Which of the following statement(s) are correct?

1. Electronic configuration of $Cr$ is $\left[Ar\right]3d^{5}4s^1$ (Atomic number of $Cr=24$).

2. The magnetic quantum number may have a negative value.

3. In the silver atom, $23$ electrons have a spin of one type and $24$ of the opposite type (Atomic number of $Ag=47$).

4. The oxidation state of nitrogen in $H{N}_3$ is $-3$.

• A. 1, 2, 3
• B. 2, 3, 4
• C. 3, 4
• D. 1, 2, 4

Answer 1

The correct option is A 1, 2, 3

The statements 1,2 and 3 are correct. The statement 4 is incorrect.
1.
Electronic configuration of Cr is $\left[Ar\right]3d^{5}4s^1$ (Atomic number of Cr=24). Both 3d and 4s orbitals are half filled. This leads to extra stability.
2.
The magnetic quantum number may have negative value.
Thus, when $l=2$, $m=-2,-1,0,+1,+2$
3.
In silver atom, 23 electrons have a spin of one type and 24 of the opposite type (Atomic number of Ag=47). It has one unpaired electrons and 23 electron pairs. Two electrons in an electron pair have opposite spin.
4.
The oxidation state of nitrogen in $H{N}_3$ is $-\frac{1}{3}$.
Let x be the oxidation number of nitrogen in $H{N}_3$. The oxidation number of H is +1.
$+1+3\left(x\right)=0$
$3x=-1$
$x=-\frac{1}{3}$