JEE Main · 2020 · Shift-IeasyATOM-125

In the sixth period, the orbitals that are filled are:

Structure of Atom · Class 11 · JEE Main Previous Year Question

Question

Options

a
$6s, 4f, 5d, 6p$
✓
b
$6s, 5d, 5f, 6p$
c
$6s, 5f, 6d, 6p$
d
$6s, 6p, 6d, 6f$

Correct Answera

$6s, 4f, 5d, 6p$

Detailed Solution

🧠 The Periodic Fill Sequence The sequence of orbitals filled in any period follows the $(n+l)$ rule. A period always starts with an $s$ -orbital and usually ends with a $p$ -orbital.

🗺️ The 6th Period Audit For $n=6$ :

Start: $6s$ ( $n+l = 6$ ).
The f-block: $4f$ ( $n+l = 4+3=7$ ).
The d-block: $5d$ ( $n+l = 5+2=7$ ). (Note: $4f$ fills before $5d$ due to lower $n$ ).
End: $6p$ ( $n+l = 6+1=7$ ). Correct Sequence: $6s, 4f, 5d, 6p$ .

⚡ The $(n+l)$ Rule Orbitals are filled in order of increasing $(n+l)$ . $6s(6) \to 4f(7) \to 5d(7) \to 6p(7)$ . Within the $7$ -ties, the lowest $n$ fills first.

⚠️ Common Traps Don't include $5f$ or $6d$ . Those belong to the $7^{\text{th}}$ period.

$\boxed{\text{Answer: (a)}}$

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