Electronegativity and Electronaffinity

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Shirley Wong 2E
Posts: 22
Joined: Fri Sep 25, 2015 3:00 am

Electronegativity and Electronaffinity

Postby Shirley Wong 2E » Thu Oct 08, 2015 2:35 pm

What is electronegativity and electron affinity? Why does it increase when you go from bottom to top and left to right on the periodic table?

Divya Prajapati 1E
Posts: 40
Joined: Fri Sep 25, 2015 3:00 am

Re: Electronegativity and Electronaffinity

Postby Divya Prajapati 1E » Thu Oct 08, 2015 7:23 pm

Electronegativity and electron affinity are basically the same concept. Electronegativity is an element's tendency to attract electrons, while electron affinity is the likelihood of an atom to gain an electron. Both properties deal with how much an element "wants" to gain an electron for greater stability.

The trends of an increase from left to right and from bottom to top can be explained using electron configurations. As we move from left to right, elements have more and more electrons in their valence shells, until reaching a full set of 8 electrons with the noble gases. Elements close to the noble gases can be considered almost there in terms of gaining their full set of electrons. Halogens like chlorine, for example, only need one more electron, while other nonmetals like oxygen, nitrogen, and carbon only need a few more electrons. As a result, all of these elements on the right side of the periodic table really "want" an electron. In other words, they have high electron affinity and are highly electronegative in comparison to elements further to the left on the periodic table. As for greater affinity/electronegativity moving from bottom to top, this corresponds to a trend in atomic radius. Larger atoms (near the bottom of the periodic table) will not have as much attraction to newly added electrons because these electrons are farther away from the nucleus. As a result, they have lower electron affinity.

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