Ionic v. Covalent Bonding

[Vivian Leung 1C]

Hi everyone,

How can you tell when to an ionic bond is formed over a covalent bond and vice versa given just a compound's molecular formula? For example, how can you tell that ammonium chloride is "held together" by ionic bonds?

[KatarinaReid_3H]

Ionic bonding is between ions. Since ammonium NH4+ is an ion and chloride Cl- is an ion, they create an ionic bond. NH4 is a radical, thus it easily gives away an electron to Chlorine ion which also is a radical and is looking to gain an extra e-. Therefore, by gaining and losing their radical electron, they become more stable. There is no need for sharing of electrons between them.

[Abril Guanes 2A]

I think something else to note is electronegativity. We know the trends for electronegativity looking at the periodic table. Ionic bonds happen between elements that have a very large electronegativity difference (so for example, opposite sides of the periodic table), but covalent bonds happen between elements that have very similar electronegativity (elements that are close by on the periodic table). So using the periodic trends, you can use the molecular formula to see whether it has ionic or covalent bonds.

[Marylyn Makar 1B]

Hi! Dr. Lavelle mentioned in one of his lectures before that if two elements are close together on the periodic table, then they will form a covalent bond. If two elements are on opposite sides of the periodic table and bind, then they will most likely form an ionic bond.

[OwenSumter_2F]

This is also seen on Sapling Q10, where it asks you to arrange 5 bonds from most ionic to most covalent. This is found by the largest differences in electronegativity, or the farther away the two atoms are on the periodic table. It is more useful to know this as a spectrum.

[Bella Bursulaya 3G]

When atoms are far away from each other on the periodic table, they will most likely form an ionic bond, such as Ca and Cl. When they are closer, they will most likely form covalent. I do want to mention that no there is no true ionic or covalent bond. Each of these characters will have a little bit of the other, i.e. ionic bonding will have a little covalent character and vice versa. Hope that helps!

[Madeline Ogden 3B]

Along with what everyone else has already said, a rough guideline for finding out if a bond is ionic or covalent is to find the difference in electronegativity between the two molecules. If the difference is greater than 2 then the bond is ionic, whereas if the difference is less than 1.5, the bond is covalent.

[Vivian Leung 1C]

I see. Thank you everyone!

[MichaelMendozaD1F]

Along with what everyone else has already said, a rough guideline for finding out if a bond is ionic or covalent is to find the difference in electronegativity between the two molecules. If the difference is greater than 2 then the bond is ionic, whereas if the difference is less than 1.5, the bond is covalent.

how do we find the difference in electronegativity?

[MichaelMendozaD1F]

how do we arrange bonds according to length?
I believe this was in the sampling hw Q11.

[Christine Ma 3L]

how do we find the difference in electronegativity?

You either find an element's electronegativity value by using an electronegativity chart or you'll be given it by the problem, since we're not expected to memorize electronegativity values. We don't need to know exact values but by looking at different elements' locations on the periodic table you should still be able to tell if a bond is likely going to be covalent or ionic (like previous responses mentioned).

[Christine Ma 3L]

how do we arrange bonds according to length?
I believe this was in the sampling hw Q11.

Bond length depends on the type of bond (single, double, triple) and the sizes of the atoms involved in the bond.

Triple bonds are shorter than double bonds which are shorter than single bonds, given the bonds being compared involve the same atoms.
For example, a carbon-oxygen single bond is longer than a carbon-oxygen double bond.

Larger atoms will have longer bonds since the internuclear distance (distance between the atoms' nuclei) is greater.
For example, a N-I bond will be longer than an N-H bond because I is a much larger atom than H.

[Tatyana Bonnet 2H]

Ionic bonds tend to be between s and p block elements. This is because of the bigger difference in electronegativity. The larger the difference in electronegativity, the more likely it is ionic. The smaller the difference, and the closer together the elements are on the periodic table, the more they are covalent.

[Jonathan Banh 1G]

In terms of your example, you have to recognize the mechanism behind the formation of the bond. In ammonium chloride, the difference in charges between NH4+ and Cl- is what attracts the two substances to each other and causes them to ionically bond with each other. It is clear here that no sharing of electrons takes place. Electronegativity is also an approach you could use in classifying types of bonds. If atoms are far apart from each on the periodic table, it denotes that there is a large difference in electronegativity between the two and thus, the bonding is likely to be ionic. However, if they are close apart, it denotes that there is little to no difference in electronegativity between them which allows you to consider the bond as covalent.

[MichaelMendozaD1F]

how do we arrange bonds according to length?
I believe this was in the sampling hw Q11.

Bond length depends on the type of bond (single, double, triple) and the sizes of the atoms involved in the bond.

Triple bonds are shorter than double bonds which are shorter than single bonds, given the bonds being compared involve the same atoms.
For example, a carbon-oxygen single bond is longer than a carbon-oxygen double bond.

Larger atoms will have longer bonds since the internuclear distance (distance between the atoms' nuclei) is greater.
For example, a N-I bond will be longer than an N-H bond because I is a much larger atom than H.

thank you !

[Madeline Ogden 3B]

Along with what everyone else has already said, a rough guideline for finding out if a bond is ionic or covalent is to find the difference in electronegativity between the two molecules. If the difference is greater than 2 then the bond is ionic, whereas if the difference is less than 1.5, the bond is covalent.

how do we find the difference in electronegativity?

I've been using an electronegativity chart because I don't think that we've been given an equation to be able to find it or anything like that. I assume on the midterm that it'll have to be given to us because at Justin's workshop on Saturday he said that an electronegativity table won't be given.

[MichaelMendozaD1F]

Along with what everyone else has already said, a rough guideline for finding out if a bond is ionic or covalent is to find the difference in electronegativity between the two molecules. If the difference is greater than 2 then the bond is ionic, whereas if the difference is less than 1.5, the bond is covalent.

how do we find the difference in electronegativity?

I've been using an electronegativity chart because I don't think that we've been given an equation to be able to find it or anything like that. I assume on the midterm that it'll have to be given to us because at Justin's workshop on Saturday he said that an electronegativity table won't be given.

ok thank you !