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Help with multiple choice chemistry question 😄

15katiesmith

I’m unsure on why the answer is C as they all increase in nuclear charge. Any help would be greatly appreciated !! X

(edited 11 months ago)

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Reply 1

eyjc

Hi Katie, I believe u practically answered ur own question lol

As you go across the period, the nuclear charge increases due to an extra proton being added.
This means that there are stronger attractive forces between the nucleus and outer e- ... so LOTS of energy is required to overcome these strong forces to remove an e- (explains why first ionisation energy increases)

Hope this helps :h:

Reply 2

simxne_

so basically, Al and S are slightly lower than the element before them - it helps to remember the overall trend on a graph of first ionisation energies across a period. Aluminium is starting to fill its 3p sub-shell ([Ne]3s23p1) and so has one electron in a 3p orbital. The 3p sub-shell is at higher energy than the 3s sub-shell so less energy will be required to remove the electron. With sulfur, electrons are starting to pair up ([Ne]3s23p4) - it already has an electron in each of its three 3p orbitals, so it's last electron has now paired up with another electron. This pairing will result in repulsion (since both electrons are negative), making it slightly easier to remove this electron and less energy is required.

Hopefully my explanation makes sense! It can help to look at orbital notations for the two elements (the boxes with the arrows representing electrons) just to visualise it too. : )