Question

Question #12702

Answer 1

Polarity is determined by the difference in Electronegativity between bonded atoms.

Explanation:

Since atoms vary in their atomic number and number of valence electrons, so does its "pull" for electrons towards its core. Which is known as Electronegativity. Think of it as how strong of a "magnet" atoms are for electrons.

So during chemical bonding (namely the Covalent Bond where atoms share electrons), the difference in the bonding atoms' Electronegativity will result in one atom pulling the (negatively charged) electron more towards it, disrupting the harmony of the electrical charge balance.

This slight asymmetry or "tilt" in the electrical charge balance will result in the molecule to have slightly negatively charged and slightly positively charged sections in its structure, making it "polar".

However, if the difference in Electronegativity is big enough, one atom will practically pull the electron to it completely, resulting in what we know as an Ionic Bond.

Please refer to these Socratic answers regarding Water Polarity and Caffeine Polarity for a few quick examples to help understand.

I hope that answered your question.

References & Further Reading:
Polarity
Electronegativity
Covalent Bond
Ionic Bond