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Electronegativity - A level AQA

Can someone please explain how the atom gets smaller across a period, there's more e-s and protons so surely it should say atoms become larger?Untitled (1).png
(edited 1 month ago)
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Original post by Rohan007best
Can someone please explain how the atom gets smaller across a period, there's more e-s and protons so surely it should say atoms become larger?Untitled (1).png

Across the period:

Proton number increases

Valence electron(s) distance from the nucleus is the same (in same shell)

Electronic shielding effect is similar

Overall there's a greater attraction between the nucleus and outermost electron(s), which is pulled in more closely, hence a smaller atom
Original post by Rohan007best
Can someone please explain how the atom gets smaller across a period, there's more e-s and protons so surely it should say atoms become larger?Untitled (1).png

As you go across the period the number of protons increases as well as electrons but because the electrons are added to the same energy level (think back to adding electrons to a ring around the nucleus to visualise) the atomic radius won't increase but since there are more protons, the nuclear charge will increase, attracting the outer electrons more strongly, therefore decreasing the size of the atomic radius (size of the atoms).
thanks so much guys
If you have any AQA chemistry questions between now and the exams send them to me and i will help you as fast as i can :smile:
Original post by ruben.greenaway
As you go across the period the number of protons increases as well as electrons but because the electrons are added to the same energy level (think back to adding electrons to a ring around the nucleus to visualise) the atomic radius won't increase but since there are more protons, the nuclear charge will increase, attracting the outer electrons more strongly, therefore decreasing the size of the atomic radius (size of the atoms).

thanks so much ru a chem student?
Original post by Rohan007best
thanks so much ru a chem student?

Yes i have my A levels in Economics, maths and chem the start of June, so if you have any questions for any of those i can also help haha
Original post by Ruben Greenaway
Yes i have my A levels in Economics, maths and chem the start of June, so if you have any questions for any of those i can also help haha

hi ruben I just had a question plz its very confusing for me. So I was taught u overcome intermolecular forces when melting something for example but u break covalent bonds when melting covalent substances for example. whats the difference between overcome and break? In the exams should I use the term overcome or break?
hi rohan, yes its a good question!
So when compounds or molecules are changing states, this involves intermolecular forces and not covalent bonding.
This is because the molecule/ compound is attached to the same things for example if you melt and then boil H2O the O-H covalent bonds still remain in solid, liquid and gas otherwise it wouldn't be water.
So the intermolecular forces are what is overcome (overcome is a more clear word to use for intermolecular forces and 'break' is often used when talking about covalent bonding).
The intermolecular forces are overcome from solid to liquid, and then further intermolecular forces that were remaining are overcome, forming a gas.
Break is used when talking about covalent bonding as it is visualised as a physical bond.
Hope that answers your question :smile:

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