Question

Out of $HF$ and ${H_2}O$ ,which is more polar and why?

Answer 1

To find which one out of $HF$ and ${H_2}O$ is more polar we first need to know the exact definition of a polar molecule. A polar molecule is usually obtained when one end of the molecule has more number of positive charges and the opposite end of the molecule has negative charges, thereby creating an electrical pole.

Complete step-by-step answer: The electronegativity between H and F is more than the electronegativity between H and O. Since oxygen is less electronegative than fluorine it attracts less electrons towards itself from Hydrogen in ${H_2}O$, as compared to Fluorine in $HF$. Therefore, this F atom slightly becomes negative and the Hydrogen atom becomes slightly positive.
Hence, we can say that $HF$ is more polar than ${H_2}O$

Additional information:
When a molecule is said to possess a polar bond, then the centre of positive charge will be on one side whereas the centre of the negative charge will be on the other side, whereas the centre of positive charge will be on the different side. The entire molecule will be a polar molecule. V-shaped molecules or pyramid-shaped are said to be polar. Polar bonds generally occur when the difference in electronegativity between the two atoms is roughly between $0.5$ and $2.0$

Note: The covalent bond in a polar molecule develops a partial ionic character when the more electronegative atom tries to pull electrons towards itself than less electronegative atom. Hence we call such bonds are known as polar covalent molecules or simply polar molecules.