Quantum Numbers and Orbitals Statement Analysis

❓ Question

Correct statements for an element with atomic number:

$$9$$

are:

A.

There can be 5 electrons for which:

$$m_s=+\frac12$$

and 4 electrons for which:

$$m_s=-\frac12$$

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B.

There is only one electron in $p$-orbital.

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C.

The last electron goes to orbital with:

$$n=2 \text{ and } l=1$$

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D.

The sum of angular nodes of all the atomic orbitals is 1.

Choose the correct answer:

1. A, C and D only
2. C and D only
3. A and C only
4. A and B only

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🖼 Question Image

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✍️ Short Explanation

This problem is based on:

👉 Electronic configuration
👉 Quantum numbers
👉 Angular nodes.

Main idea:

Atomic number:

$$9$$

corresponds to:

$$\boxed{ F(Fluorine) }$$

Electronic configuration:

$$1s^2\,2s^2\,2p^5$$

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🔷 Step 1 — Check Statement A 💯

Configuration:

$$1s^2\,2s^2\,2p^5$$

Using Hund’s rule:

In:

$$2p^5$$

three electrons first occupy separately with parallel spins.

Total spin distribution becomes:

$$5 \text{ electrons with } m_s=+\frac12$$

and

$$4 \text{ electrons with } m_s=-\frac12$$

Hence:

$$\boxed{ \text{Statement A is TRUE} }$$

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🔷 Step 2 — Check Statement B

Configuration contains:

$$2p^5$$

Thus there are:

$$5$$

electrons in $p$-orbitals.

So statement:

“Only one electron in $p$-orbital”

is false.

$$\boxed{ \text{Statement B is FALSE} }$$

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🔷 Step 3 — Check Statement C

Last electron enters:

$$2p$$

orbital.

For $p$-orbital:

$$l=1$$

and principal quantum number:

$$n=2$$

Thus:

$$\boxed{ \text{Statement C is TRUE} }$$

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🔷 Step 4 — Check Statement D

Angular nodes:

$$=l$$

Orbitals occupied are:

$1s$

$$l=0$$

Angular nodes:

$$0$$

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$2s$

$$l=0$$

Angular nodes:

$$0$$

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$2p$

$$l=1$$

Angular nodes:

$$1$$

Total angular nodes:

$$0+0+1=1$$

Hence:

$$\boxed{ \text{Statement D is TRUE} }$$

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🔷 Step 5 — Final Correct Statements

$$\boxed{ A,\ C,\ D }$$

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🔷 Step 6 — JEE Trap Alert 🚨

❌ $2p^5$ ko one electron samajh lena

❌ Angular nodes formula bhool jaana

❌ Last electron orbital identify na kar paana

Remember:

$$\boxed{ \text{Angular nodes}=l }$$

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✅ Final Answer

$$\boxed{{\displaystyle \text{A, C and D only}}}$$

(Option 1)

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