Ionisation energies

' State the general trend in first i.e from carbon to neon.
Deduce the element that deviates from this trend and explain why this element deviates from the trend'

I got one mark for saying an increase
the element which deviates is oxygen and the explanation was 'paired electrons in a 2p orbital so the paired electrons repel'
ik this may sound really stupid but aren't there paired electrons in all the elements from carbon to neon? why is it oxygen and can someone please explain the explanation from the mark scheme to me. thank you

Reply 1

Exdoz

Original post by PastelColours

Carbon and nitrogen dont have paired electrons in the p-orbital. It is 2p2 and 2p3 respectively. From oxygen, they have paired electrons in p-orbital- 2p4

Reply 2

PastelColours

Original post by Exdoz

Carbon and nitrogen dont have paired electrons in the p-orbital. It is 2p2 and 2p3 respectively. From oxygen, they have paired electrons in p-orbital- 2p4

Thank you but what does it mean by 'paired electrons' thats the bit which is confusing me! sorry to bother you once again x

Reply 3

Exdoz

Original post by PastelColours

Thank you but what does it mean by 'paired electrons' thats the bit which is confusing me! sorry to bother you once again x

Think of it as a bus analogy. If you go on the upper deck and there are some empty seats and some seats where it is free next to other passengers, where will you sit? You will sit where it is empty right- so you wont sit next to the passenger. Same thing for these electrons. As there are 3 p-orbitals, they will fill them up 'single-handedly' before pairing up in the same orbital. So if there are 4 electrons, the first 3 will single handedly fill up the 3 orbitals, and then the last one is forced to go and pair with one of the electrons in the p-orbital. *Orbitals can hold a maximum of 2 electrons at once*

Reply 4

JamesAndrews1

Original post by Exdoz

And orbitals are filled singularly because electrons repel 1 another as they have the same charge (-ve). Thus meaning it makes sense and the atom is more stable when electrons occupy each orbital singularly first before pairing.

Reply 5

Exdoz

Original post by JamesAndrews1

I wouldn't say it makes the atom more stable (I haven't learnt that). But you get the idea.

Reply 6

klopp

oxygen is just above sulfur in periodic table
sulfur has paired electrons in its p orbital which means oxygen has it tooo

Reply 7

PastelColours

Original post by Exdoz

Ah ok that bus analogy works ty so much x

Reply 8

JamesAndrews1

Original post by Exdoz

I wouldn't say it makes the atom more stable (I haven't learnt that). But you get the idea.

It does make the atom more stable. Think about it, if the electrons were paired in an orbital they'd repel 1 another and be removed more easily. Thus the atom would want to release the electron and the reaction that follows will make it more stable. However, singularly paired electrons would make the atom more stable (less reactive)

Reply 9

Exdoz

Original post by JamesAndrews1

It would actually be less stable. Because to remove that electron, you would need less energy, due to 'mutual repulsion'- it will have a lower ionisation energy than an element that is close to its atomic number without a paired electron in the p-orbital. As less energy is needed- it is less stable