Chemistry

ATOMIC AND IONIC RADIUS

This page explains the various measures of atomic radius, and then looks at the way it varies around the Periodic Table - across periods and down groups. It assumes that you understand electronic structures for simple atoms written in s, p, d notation. | |
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|       |Important!  If you aren't reasonable happy about electronic structures you should follow this link|
|       |before you go any further.                                                                         |
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|ATOMIC RADIUS                                                                                             |
|Measures of atomic radius                                                                                 |
|Unlike a ball, an atom doesn't have a fixed radius. The radius of an atom can only be found by measuring   |
|the distance between the nuclei of two touching atoms, and then halving that distance.                     |
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|As you can see from the diagrams, the same atom could be found to have a different radius depending on     |
|what was around it.                                                                                       |
|The left hand diagram shows bonded atoms. The atoms are pulled closely together and so the measured radius|
|is less than if they are just touching. This is what you would get if you had metal atoms in a metallic   |
|structure, or atoms covalently bonded to each other. The type of atomic radius being measured here is     |
|called the metallic radius or the covalent radius depending on the bonding.                               |
|The right hand diagram shows what happens if the atoms are just...