Ionic vs Covalent Bonds

[Sarah Huang 3A]

Hi!

As we've been going through this unit/module, I've been wondering when you know a bond is ionic or covalent when you are drawing a Lewis structure? Like I know the H2O is a covalent bond and that NaCl is an ionic bond, but how would you know for other molecules?

[vanessanguyen3I]

You have to compare the electronegativity levels between the two elements that are bonded. As a guideline, Professor Lavelle stated that if there is a difference greater than 2 it is ionic, and if it has a difference of less than 1.5 it is covalent.

[Annie Tong 2G]

One way to check if it's an ionic or covalent bond is through electronegativity. If the electronegativity values of the two atoms differ by more than 2, it has so much ionic character that it's considered an ionic bond. If the difference is less than 1.5, it has so much covalent character that it's a covalent bond.

Another way of checking is simply looking at the distance between the two atoms on the periodic table. If the atoms are very far apart from each other, chances are that it's ionic. If they're close together (especially on the right side of the table), chances are that it's covalent.

[allyssa bradley 1H]

I agree with this! Also, I think it is worth mentioning that polar covalent bonds exist where the electrons are unequally shared, so the difference between ionic and covalent is kind of a case-by-case situation or a spectrum rather than having a specific rule. Vanessa's mention of the electronegativity is also very helpful!

[Kelly Tran 1J]

To determine whether a bond is ionic or covalent, you can calculate the electronegativity difference between 2 atoms. If the difference is >2, it is an ionic bond. If the difference is <1.5, it is a covalent bond. Typically the bond between elements in the far left and far right of the periodic table are ionic.

[America Ramirez 3H]

You can tell from either the difference in electronegativity or how far away each atom in the molecule is from the periodic table.
If there is an electronegativity difference greater than 1.5 then that bond is ionic.

[vanessanguyen3I]

It depends on the difference in electronegativity between the atoms bonded! Also, it's useful to remember that most molecules have some form of ionic character (polarity), and most ionic compounds have some form of covalent character (depolarization), so it's not entirely black and white. Hope this helps.

[CesarLec1]

By comparing electro negativities, if you do not have a chart of their electro negativities handy, then by looking at the periodic table can help you. The further away the elements are from each other, like on the opposite side, then they are most likely ionic but if they are close to each other then they are most likely covalent.

[Bai Rong Lin 2K]

When determining if it's a ionic bond or a covalent bond, I would first try to determine the difference in electronegativity.

[Adam_ElSayed_3B]

As others have said, compare electronegativity, but I find that it helps to recognize that salts and metals will almost always be ionic.