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Chemistry electronegativity

Why is chlorine more electronegative that sodium?
I can't get my head around this so any help would be appreciated!
Original post by murrayma767
Why is chlorine more electronegative that sodium?
I can't get my head around this so any help would be appreciated!


Although both elements are in the third period, Chlorine has seven and sodium one electron on the valance shell. That is to say that chlorine needs just one another electrone to be completed on that shell, sodium compared to it seven. (octet rule). Thus chlorine has a higher effective nuclear charge (+7) than sodium (+1) That is the reason why chlorine's electrons have a stronger attraction to the one electron on the valence shell of the sodium. Chlorine in reaction with sodium tries to get the state of noble gas configuration.
(edited 6 months ago)
Reply 3
Original post by murrayma767
Why is chlorine more electronegative that sodium?
I can't get my head around this so any help would be appreciated!

Electronegativity is the "tendency of an atom to attract a bonding pair of electrons".

If we think about the nucleus, Cl has 17 protons, whereas Na has 11. This effectively means that Cl has a greater nuclear charge than Na. Greater positive charge –> better at attracting electrons.

This is the main difference between Na and Cl affecting the difference in electronegativity. There are a couple of other factors which also affect electronegativity (think size, and "screening" from inner electrons) see https://chemguide.co.uk/atoms/bonding/electroneg.html for more info.

These general concepts also come up when you're looking at ionisation energies (https://www.chemguide.co.uk/atoms/properties/ies.html) :smile:

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