Atomic Sizes Chart: All Elements in Periodic Table

[PH7SICS]

The following link shows how to calculate the size of an atom, where can I find a chart where this has been done for all the elements in the periodic table? I know you can get charts of atomic radius but those are based on the distance between the nucleus of two bonded atoms and therefore the radius is slightly less then the actual radius. Basically I,m looking for a chart which most accurately displays the sizes of atoms.

http://hyperphysics.phy-astr.gsu.edu/hbase/particles/atomsiz.html

 

[Astronuc]

www.webelements.com

Try this page

http://www.webelements.com/webelements/properties/text/image-line/bond-length-elem.html

 

[Gokul43201]

I like this representation (also from webelements): http://www.webelements.com/webelements/properties/text/image-balls/atomic-radius-emp.html

 

[tabchouri]

I like this representation (also from webelements): http://www.webelements.com/webelements/properties/text/image-balls/atomic-radius-emp.html

It's interesting, the radius of atoms dicreases with the electronic orbit beeing filled, contrary to intuition.
And it's pretty homogeneous overs all orbits.
Anyone could explain why ?

-----------------------------------------------------
Correct me if I am wrong.
http://ghazi.bousselmi.googlepages.com/présentation2

 

[DaveC426913]

I like this representation (also from webelements): http://www.webelements.com/webelements/properties/text/image-balls/atomic-radius-emp.html

Why are there no representations of the noble gases?

 

[Gokul43201]

Why are there no representations of the noble gases?

The atomic sizes are derived from various bond lengths. The noble gases do not form bonds with other elements or among themselves (at least not very well) because of their inertness, making it very difficult to determine a covalent radius.

 

[cesiumfrog]

The atomic sizes are derived from various bond lengths.

Is a H2 molecule really that much smaller than, well, every other atom and diatom?

 

[DaveC426913]

The atomic sizes are derived from various bond lengths.

Ah. That's what I suspected.

So, these aren't really reps of the diameter of the outermost shell i.e. the "physical" size, they're reps of the operating diameter of the atom?

 

[Gokul43201]

Is a H2 molecule really that much smaller than, well, every other atom and diatom?

Actually, the He-atom is smaller than the H-atom, as should be expected. Also, since atomic radii can be very crudely expected to go like some rapidly increasing function of the principal quantum number of the valence shell (the significant variation along a period is evidence for the crudeness), the relative sizes down a group show the largest variation at the top of the group. For simplicity, if the radius went like n², then we'd expect R(H)/R(Li) ~ 1/4 (measured value 0.26) , while R(Na)/R(K) ~ 9/16 (measured value 0.8) and R(Rb)/R(Cs) ~ 25/36 (measured value 0.9).

 

[Gokul43201]

It's interesting, the radius of atoms dicreases with the electronic orbit beeing filled, contrary to intuition.

That depends on how well-developed your intuition is.

And it's pretty homogeneous overs all orbits.
Anyone could explain why ?

Going right along a period involves a small increase in the atomic number. Increasing the number of valence electrons might be expected to increase the atomic radius, but increasing the number of protons at the same rate should then be expected to cause a decrease in radius. So, to a first order in intuition, there should be no change in radius along a period.

A better intuition to use is that of the effective (screened) nuclear charge. Hopping by one atom to the right increases the number of protons and electrons by 1. The additional electron can not completely screen the charge of the additional proton, resulting in a net increase in the nuclear attraction to the outer electrons.

 

[PH7SICS]

The data given my web elements varies considerably depending on how the atomic radius was derived. I don't know if any of those values given were obtained using the calculation in the link I provided. I notice that all the values have been rounded up so I'm guessing its not the most accurate chart. In any case dose anyone know which value is most accurate ie which method?

 

[cesiumfrog]

Actually, the He-atom is smaller than the H-atom, as should be expected. Also, since atomic radii can be very crudely expected to go like some rapidly increasing function of the principal quantum number of the valence shell (the significant variation along a period is evidence for the crudeness), the relative sizes down a group show the largest variation at the top of the group. For simplicity, if the radius went like n², then we'd expect R(H)/R(Li) ~ 1/4 (measured value 0.26) , while R(Na)/R(K) ~ 9/16 (measured value 0.8) and R(Rb)/R(Cs) ~ 25/36 (measured value 0.9).

Does that really explain why the chart you mentioned depicts H as only a point, compared to the other atoms depictions? I wondered if they were trying to represent the size of a hydrogen ion.

 

[Gokul43201]

Does that really explain why the chart you mentioned depicts H as only a point, compared to the other atoms depictions? I wondered if they were trying to represent the size of a hydrogen ion.

I suspect that's either an artifact of the picture resolution or an error of carelessness. The H-atom ought to be only a little smaller than the F-atom (last ball in the second period). There would be no sense in representing the size of the H+ ion (a proton) in that chart.