JEE Chemistry 2025 Question with Solution

Given: Atom in ground state with $Z = 24$.

Find: Number of electrons with azimuthal quantum numbers $l = 1$ and $l = 2$.

For chromium, the ground state electronic configuration is

$$1s^2\,2s^2\,2p^6\,3s^2\,3p^6\,3d^5\,4s^1$$

Now use the subshell relation:

• $s$ subshell corresponds to $l = 0$
• $p$ subshell corresponds to $l = 1$
• $d$ subshell corresponds to $l = 2$

Electrons with $l = 1$ are the electrons in $p$ subshells:

$$2p^6 + 3p^6 = 6 + 6 = 12$$

Electrons with $l = 2$ are the electrons in $d$ subshells:

$$3d^5 = 5$$

Therefore, the number of electrons with azimuthal quantum numbers $l = 1$ and $l = 2$ are $12$ and $5$ respectively. The correct option is C.

Given: Ground state atom with $Z = 24$.

Find: Electrons having $l = 1$ and $l = 2$.

First identify the element: $Z = 24$ is chromium.

Its ground state configuration is

$$1s^2\,2s^2\,2p^6\,3s^2\,3p^6\,3d^5\,4s^1$$

Now count by azimuthal quantum number.

For $l = 1$, count all $p$-electrons:

• $2p^6$ gives $6$ electrons
• $3p^6$ gives $6$ electrons

So,

$$6 + 6 = 12$$

For $l = 2$, count all $d$-electrons:

• $3d^5$ gives $5$ electrons

So, electrons with $l = 2$ are

$$5$$

Hence the required numbers are $12$ and $5$. Therefore, the correct answer is 12 and 5, that is, option C.