Answer:
difference in the atoms' electronegativites
Step-by-step explanation:
The measure of an atom's ability to attract electrons is called electronegativity. Electronegativity is a measure of the tendency of an atom to attract a bonding pair of electrons. Electronegativity increases from left to right across a row in the periodic table while electronegativity decreases down the group because the bonding pair of electrons is increasingly distant from the attraction of the nucleus. A small electronegativity difference leads to a polar covalent bond. A large electronegativity difference leads to an ionic bond.
To find the electronegativity difference between two atoms, subtract the smaller electronegativity from the larger one to find the difference.
1. If the difference is below about 0.5, the bond is nonpolar covalent
2. If the difference is between 0.5-1.6, the bond is polar covalent.
3. If the difference is over 2.0, the bond is ionic.
4. If the difference is between 1.6-2.0, check for a metal. If there is a metal in the bond, the bond is ionic. If there are only non-metals, the bond is polar covalent.