Year 12s: what will be the first way you research your future options? >>

Ionic or covalent?

I thought that ionic bonds are formed when the electronegativity difference between two atoms is > 1.8, so how is the bond between zinc and chlorine ionic in Zinc Chloride if the electronegativity difference between Zinc and chlorine is 1.6?

Reply 1

ChemistryWebsite

Original post by thedecorator33

The difference in electronegativity values you quote is just a guide for reference, rather than a rule that atoms / ions must obey.

Reply 2

thedecorator33

Original post by TutorsChemistry

The difference in electronegativity values you quote is just a guide for reference, rather than a rule that atoms / ions must obey.

So how do I know if a bond will be ionic or covalent?

Reply 3

charco

Study Forum Helper

Original post by thedecorator33

So how do I know if a bond will be ionic or covalent?

Learn a few patterns.

Most metal chlorides are ionic unless the charge density on the metal ion is large, such as ions with a 3+ charge or higher oxidation states.

Hence, tin(II) chloride is ionic whereas tin(IV) chloride is covalent.

The chloride ion is large and polarisable so the chlorides of 2+ charge metals will have an appreciable degree of covalent character.