Question: Which element has a larger radius?

[principe]

Okay so I've been taught that Group VIII elements, the inert gases, are ignored when it comes to the periodic table trends. But the TSSM 2007 trial exam suggests that Fluorine has a larger radius than Neon. The question asks to: Rank the following elements in order of atomic size, number 1 being the largest. The elements are Sodium, Neon and Fluorine.
TSSM's response was: Sodium(1), Fluorine(2) and Neon(3)
My answer was: Sodium(1), Neon(2) and Fluorine(3)
Is there like another special rule that I'm missing? Or is it just a misprint? I won't be seeing my Chemistry teacher for a while so yeah.

[ninwa]

atom sizes decrease across a period - I think that applies to inert gases too? cos F and Ne have the same no. of shells but Ne has a greater core charge - therefore electrons are more strongly attracted etc

[bilgia]

i think im getting confused...dont grp8 elements all have full outershells? how can they attract electrons??

[ninwa]

i think im getting confused...dont grp8 elements all have full outershells? how can they attract electrons??

no no sorry, i wasn't clear lol, i meant the nucleus of the atom attracts the atom's electrons (electrostatic attraction)

[principe]

i think im getting confused...dont grp8 elements all have full outershells? how can they attract electrons??

Yeah that's what I've been taught as well. Also, when I did my written report on trends across the periodic table, this site (which seemed pretty reliable), also stated that group 8 elements are unaffected by the atomic radius trend. Example: Argon would be larger than Chlorine.
There was another exam that asked a similar question, which element has the largest atomic radius?, except the elements were Chlorine and Argon. The correct answer was Argon. So it's kind of confusing if the correct responses contradict each other.

[Collin Li]

You will not be asked to compare group VIII elements with the other 7 groups.

[BA22]

The element of suprise

Its radius traps all.

[principe]

You will not be asked to compare group VIII elements with the other 7 groups.

Okay then, that's a bit of a relief. But I still don't understand the concept behind it.

[ezflow]

How do you quote people?

principe, the concept behind the group VIII elements is the same as the other 7... It has to do with how strongly the outer-shell electrons are pulled into the nucleus ---> core charge.

i.e. Neon has a higher core charge than Fluorine. Neon has 8 electrons in the outer-shell and Fluorine only has 7, but they are both in the same shell. etc. etc. etc. etc.

[principe]

How do you quote people?

principe, the concept behind the group VIII elements is the same as the other 7... It has to do with how strongly the outer-shell electrons are pulled into the nucleus ---> core charge.

i.e. Neon has a higher core charge than Fluorine. Neon has 8 electrons in the outer-shell and Fluorine only has 7, but they are both in the same shell. etc. etc. etc. etc.

Lol there's a quote button on the top right of each post. Anyways, yeah that's pretty much all I know, the increasing core charge would have a stronger pull on the electrons hence reducing the atomic radius. But yeah some exam solutions state that this rule is ignored when it comes to Group VIII elements, so I got confused. Hopefully it doesn't appear in this year's exam.

[hifer]

The answer lies in the fact that for elements other than the noble gases, you are measuring metallic or covalent radius, which is measured when they form metallic or covalent bonds. For nobles gases, we measure their van der Waals(Dispersion forces) radius, where they are bonded less tightly and closely to each other.

To explain this simply, when non-group 8 elements form metallic or covalent bonds, their electron "cloud" gets squashed, and since the atomic radius measures the distance from the nucleus to the center electrons that participate in the bonding, they are smaller than the noble gases in their period.

[joechan521]

The answer lies in the fact that for elements other than the noble gases, you are measuring metallic or covalent radius, which is measured when they form metallic or covalent bonds. For nobles gases, we measure their van der Waals(Dispersion forces) radius, where they are bonded less tightly and closely to each other.

To explain this simply, when non-group 8 elements form metallic or covalent bonds, their electron "cloud" gets squashed, and since the atomic radius measures the distance from the nucleus to the center electrons that participate in the bonding, they are smaller than the noble gases in their period.

i agree, top answer

[hifer]

The answer lies in the fact that for elements other than the noble gases, you are measuring metallic or covalent radius, which is measured when they form metallic or covalent bonds. For nobles gases, we measure their van der Waals(Dispersion forces) radius, where they are bonded less tightly and closely to each other.

To explain this simply, when non-group 8 elements form metallic or covalent bonds, their electron "cloud" gets squashed, and since the atomic radius measures the distance from the nucleus to the center electrons that participate in the bonding, they are smaller than the noble gases in their period.

i agree, top answer

wahaha.. joe u dun even do chem :p lol

[Collin Li]

I maintain that this isn't on the course.

[hifer]

Yup, agreed it's not on the course.

But i just found this question pretty intriguing and posted the answer for anyone that's actually interested afterall, it's not all about getting the marks is it? haha..  :lol: