Video: Comparing Electronegativity of Elements by Using the Periodic Table

From their positions on the periodic table, which of the following has the highest electronegativity? [A] Co [B] B [C] Cl [D] Mg [E] P

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Video Transcript

From their positions on the periodic table, which of the following has the highest electronegativity? A) Co, B) B, C) Cl, D) Mg, or E) P.

Before we pick out their positions, we should look at the names. We have cobalt, boron, chlorine, magnesium, and phosphorus. Let’s locate them on the periodic table. Cobalt can be found in period four in group nine. It’s a d block element in the first transition series. Boron is a group 13 element in period two. Chlorine can be found in group 17 just below fluorine in period three. All the way to the other end of period three, we find the alkaline earth metal magnesium in group two. And lastly, we have phosphorus, still in period three, but in group 15.

The next part of the question is remembering what electronegativity is. Electronegativity is a measure of the ability of atoms to attract electrons in bonds. The most popular scale for electronegativity is the Pauling scale, which gives elements a number between zero and four. High numbers on this scale indicate that atoms of an element will strongly attract electrons in bonds, while a low number means a week attraction.

When elements are arranged to the periodic table, their electronegativities show a general trend, increasing left to right and bottom to top. On this basis, we would expect low electronegativity values for magnesium and cobalt, given that they are much further to the left, or much lower than the other elements. Meanwhile, boron and phosphorus, being further to the right and further up, are going to have higher electro negativities. But chlorine being closest to the top-right hand column will probably have the highest electronegativity of the five.

So, based purely on their positions on the periodic table, chlorine wins out with the highest electronegativity. It’s easy to find the actual numbers for the electronegativities of the elements. Chlorine has an electronegativity of 3.16. Phosphorus has a value of 2.19. Boron, 2.04; cobalt, 1.88; and the lowest, magnesium, at 1.31. So, we can confidently say that out of the five, the element with the highest electronegativity is chlorine.

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