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Updated on : 2022-09-05

Solution

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Correct option is B)

**Hint:** Aufbau principle states that electrons getting filled in the orbitals in the increasing order of energy.

**Step 1: The energy of an orbital is directly proportional to the ****$(n+l)$ value.**

**The $(n+l)$ value for $2s$ level:**

For **$2s$ **energy level-

**$n=2$**

Where $n$ is the principal quantum number and $l$ is the azimuthal quantum number.

For $s$ orbital, $l=0$

So, **$(n+l)=2+0$ **

**$(n+l)=2$ **

**Step 2:**

**The $(n+l)$ value for $2p$ level:**

**For $2p$ energy level-**

$n=2$

Where $n$ is the principal quantum number and $l$ is the azimuthal quantum number.

For $p$ orbital, $l=1$

So, **$(n+l)=2+1$ **

**$(n+l)=3$ **

**Step 3:**

Comparison of $(n+l)$ value of two energy levels:

As the value of $(n+l)$ for $2s$ orbital is less than that of $2p$ orbital so $2s$ orbital has lower energy than $2p$ orbital. Therefore $2s$ orbital will get filled first then $2p$ orbital will starts filling.

**Final answer:**

**So the orbital diagram in which Aufbau principle is violated is option (B).**

**So the correct option is (B).**

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