Identifying Ionic vs Covalent

[Eileen Si 1G]

How do you identify whether a bond is ionic or covalent (polar or nonpolar)? And is it possible to tell by just looking at a molecular formula?

[Selena Yu 1H]

You can identify that a bond is ionic because electrons are being transferred from metal to nonmetal atoms, while a bond is covalent because electrons are being shared instead of being transferred.

[Tyler Angtuaco 1G]

Ionic compounds are formed from the combination of a metal and a non-metal, in which the metal is written first in the molecular formula. Covalent compounds are those which consists of covalent bonds, which only result between two non-metals. Another tip in distinguishing between them is through their Lewis structures: ionic compounds are written by denoting the cation and anion separately (the metal and non-metals with their respective charges and brackets around the element with the negative charge), while covalent compounds are written with a shared pair of electrons in between.

[Justin Quan 4I]

To add on, comparing the electronegativity between atoms is the general way to tell if what type of bonds the molecule will form. Typically a greater difference in electronegativity would mean an ionic bond will form. A small difference, for example around 0.5, would result in non-polar covalent bond. Any difference in between would typically form polar covalent bonds.

[Julia Mazzucato 4D]

We will also be able to look at formal charges within the molecule to determine polarity of a covalent bond.

[Katherine Chhen 3I]

We will also be able to look at formal charges within the molecule to determine polarity of a covalent bond.

How would we be able to determine the polarity of a covalent bond using formal charges?

[Alan Wu]

Difference in electronegativity:
0.0 - 0.4: non-polar covalent bond
0.4 - 1.8: polar covalent bond
>1.8: ionic bond

These numbers can vary from source to source, but you get the general idea.

[Madeline Phan 1E]

Covalent bonds form between non-metal atoms as they are more similar in electronegativity, while ionic bonds form between non-metals and metals as they have extremely different levels of electronegativity.