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NEET CHEMISTRYStructure of AtomMedium

Question

If the principal quantum number n=6, the correct sequence of filling of electrons will be:

A

ns → np → (n-1)d → (n-2)f

B

ns → (n-2)f → (n-1)d → np

C

ns → (n-1)d → (n-2)f → np

D

ns → (n-2)f → np → (n-1)d

Step-by-Step Solution

According to the Aufbau Principle, orbitals are filled in the order of increasing energy, which is determined by the (n+l)(n+l) rule. For the 6th period (n=6n=6), the orbitals involved are 6s,4f,5d,6s, 4f, 5d, and 6p6p. We calculate their (n+l)(n+l) values:

  1. ns (6s): n=6,l=0⇒n+l=6n=6, l=0 \Rightarrow n+l = 6
  2. (n-2)f (4f): n=4,l=3⇒n+l=7n=4, l=3 \Rightarrow n+l = 7
  3. (n-1)d (5d): n=5,l=2⇒n+l=7n=5, l=2 \Rightarrow n+l = 7
  4. np (6p): n=6,l=1⇒n+l=7n=6, l=1 \Rightarrow n+l = 7

When (n+l)(n+l) values are equal (as with 4f,5d,6p4f, 5d, 6p), the orbital with the lower nn value has lower energy and is filled first. Therefore, the order is 4f<5d<6p4f < 5d < 6p.

Combining with 6s6s, the correct filling sequence is: 6s→4f→5d→6p6s \to 4f \to 5d \to 6p, which corresponds to the general form: ns→(n−2)f→(n−1)d→npns \to (n-2)f \to (n-1)d \to np.

Exam Context & Concepts Covered

This question aligns with the NEET CHEMISTRY syllabus, specifically targeting concepts from Structure of Atom. Mastering this topic is crucial for scoring well in the upcoming medical entrance examinations. Solving conceptually related problems will help you understand the nuances of these concepts and improve your problem-solving speed.

CHEMISTRYStructure of Atomprincipalquantumnumbercorrectsequence

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