If AB_{4} molecule is a polar molecule, a possible geometry of AB_{4} is :

(1) Square pyramidal

(2) Rectangular planar

(3) Square planar

(4) Tetrahedral

**Ans. (1)** Square pyramidal

**Sol.** For AB_{4} compound possible geometry are

S. No. | Bond pair | Lone pair | Total | Hybridisation | Geometry | Polarity |
---|---|---|---|---|---|---|

1 | 4 | 0 | 4 | sp^{3} | Tetrahedral | non polar |

2 | 4 | 1 | 5 | sp^{3}d | Sea-saw | polar |

3 | 4 | 2 | 6 | sp^{3}d^{2} | Square Planar | non polar |

Square pyramidal can be polar due to lone pair moment as the bond pair moments will get cancelled out.