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JEE Main 2025 Apr 2 Shift 1, Chemistry Q20: Valence Bond Theory And Hybridisation

JEE Main2025Apr 2, Shift 1Chemistry
Q.

A molecule with the formula has all it's elements from p-block. Element A is rarest, monoatomic, non-radioactive from its group and has the lowest ionization enthalpy value among A, X and Y. Elements X and Y have first and second highest electronegativity values respectively among all the known elements. The shape of the molecule is :

  1. A

    Square pyramidal

  2. B

    Octahedral

  3. C

    Pentagonal planar

  4. D

    Trigonal bipyramidal

Solution

Decoding the clues:

Element A: p-block, monoatomic, non-radioactive and rarest in its group with the lowest ionisation enthalpy — this is xenon (Xe).

Elements X and Y: first and second highest electronegativities in the periodic table — fluorine (F) and oxygen (O), respectively.

So the molecule is , i.e. .

Geometry of : Xenon has 8 valence electrons; 4 bond to F, 1 forms a double bond (or polar bond) to O, leaving 1 lone pair. Steric number , giving hybridisation with octahedral electron geometry. The single lone pair occupies one of the six positions; the four F atoms occupy the equatorial plane, and the O sits at the position trans to the lone pair.

The resulting molecular shape is square pyramidal.

Option (1) is correct.

Concept behind this question

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