Electronegativity

Hey everyone, welcome to this Mometrix video over electronegativity.

Let’s jump right into it. Electronegativity measures how strongly atoms pull or attract electrons to themselves to form chemical bonds.

So, the higher the electronegativity of an atom, the stronger the atom’s pull or attraction for electrons.

The electronegativity of an atom is more of a measure of an atom as a part of a molecule. It is not an intrinsic measure of an atom by itself. The reason is because the electronegativity of an atom varies based on the atom’s surroundings or environment. Atoms, however, typically do exhibit alike behavior regardless of their surroundings, but there is slight variation.

• Covalent bond are formed when two atoms, with the same electronegativity, bond together.
• Polar covalent bonds are formed when a highly electronegative atom, and an atom with a lower electronegativity form.
• An ionic bond is formed when two atoms have extremely different electronegativities, and one atom basically steals the bonded electrons from the other atom.

You can tell what type of bond will be formed between two atoms by calculating the difference in their electronegativities. For example, O₂ is joined by a covalent bond, because there is no difference in their electronegativities. If two atoms have a difference in electronegativities are below 0.5 then they will be joined by a covalent bond. If the difference in the electronegativities of two atoms is between 0.5 and 1.6, then they will be joined by a polar covalent bond. If the difference is over 2.0, then the bond is ionic. Now, here is something that is important to note: if the difference in electronegativity is somewhere between 1.6 and 2.0, then check to see if one of the elements is a metal. If there is a metal involved then the bond is ionic, if both are non-metals then the bond is polar covalent.

When looking at the elements on the periodic table, there is a trend in electronegativity. However, this trend does not take place among the noble gases. From left to right, electronegativity typically increases across the periodic table, but decreases as you move down the periodic table. This is, because there is a distance between the valence electron, and the atom’s nucleus.

The element with the highest electronegativity on the periodic table is fluorine, the element with the lowest electronegativity is francium.

Let’s do a quick review:

• Electronegativity measures how strongly atoms pull electrons towards themselves in a chemical bond.
• The higher the difference in electronegativity is between two atoms, then the more polar the bond is between them.

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