NEETChemistryChemical Bonding and Molecular Structure
A neutral covalent molecule AX _n (where X is a monovalent halogen atom) is experimentally found to have a 'see-saw' shape. Which of the following statements correctly describes the central atom A?
Options
- AIt possesses 4 bond pairs and 2 lone pairs, and belongs to Group 18 of the periodic table.
- BIt possesses 4 bond pairs and 1 lone pair, and belongs to Group 16 of the periodic table.
- CIt possesses 4 bond pairs and 0 lone pairs, and belongs to Group 14 of the periodic table.
- DIt possesses 5 bond pairs and 0 lone pairs, and belongs to Group 15 of the periodic table.
Correct answer
B. It possesses 4 bond pairs and 1 lone pair, and belongs to Group 16 of the periodic table.
Step-by-step solution
The 'see-saw' shape is a derivative of the trigonal bipyramidal electron geometry, which corresponds to a steric number of 5 ( sp ^3 d hybridisation). For a molecule AX _n to have a see-saw shape, it must have 4 bond pairs ( n=4 ) and 1 lone pair on the central atom A. Since X is a monovalent halogen, each bond pair requires one valence electron from the central atom A. The lone pair requires two valence electrons. Total valence electrons on A = 4 (for bonds) + 2 (for the lone pair) = 6. Elements with 6 valence ele