JEE Main · 2019 · Shift-ImediumPERI-011

The group number, number of valence electrons, and valency of an element with atomic number 15, respectively, are:

Classification of Elements & Periodicity · Class 11 · JEE Main Previous Year Question

Question

The group number, number of valence electrons, and valency of an element with atomic number 15, respectively, are:

Options
  1. a

    15, 6 and 2

  2. b

    16, 6 and 3

  3. c

    16, 5 and 2

  4. d

    15, 5 and 3

Correct Answerd

15, 5 and 3

Detailed Solution

🧠 Z=15Z = 15 is Phosphorus — p-block, Group 15 Phosphorus: 1s22s22p63s23p31s^{2}\,2s^{2}\,2p^{6}\,3s^{2}\,3p^{3}. Valence electrons =3s2+3p3=5= 3s^{2} + 3p^{3} = 5. Group =15= 15.

🗺️ Find valency Valency = electrons needed to complete the octet =85=3= 8 - 5 = 3.

So: Group 15, valence electrons 5, valency 3.

"Note: Phosphorus can also exhibit valency of 5 by utilising empty 3d orbitals, but its common/principal valency is 3"

Variable Valency: Unlike s-block elements, many p-block elements exhibit variable valencies due to the involvement of d-orbitals and, for heavier elements, the Inert Pair Effect. p-block elements can sometimes exceed a valency of 4 by using empty d-orbitals (for elements in period 3 and below), allowing them to form 5 or 6 bonds (e.g., \cePCl5\ce{PCl5}, \ceSF6\ce{SF6})

Answer: (d)\boxed{\text{Answer: (d)}}

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