Here, we will discuss about the different types of radii of atom and how to explain them.
What is atomic radii : types of radii
Atomic radii is the distance between the centre of the nucleus to the outermost shell containing electrons.
What is covalent radii
It is one half of the distance between the nuclei of 2 covalently bonded atoms of the same element in a molecule. For example non metals.
In case of homo-atomic diatomic molecule, r covalent = 1/2 [ Bond length ]
For example the internuclear distance between 2 atoms of H2 molecule = 74 pm. But the rcovalent = 37 pm
What is Van der Waals radius : types of radii
- It is one half of the distance between the nuclei of 2 non bonded atoms of the same element in a molecule. For example inert gas radius.
- Since, the Van der Waal’s forces of attraction are weaker than covalently bonded atoms.
- Therefore, Van der Waal ‘s radii is larger than covalent radii.
How to explain metallic radius
- Metallic bond is the simultaneous force of attraction between the mobile electrons and metal ions. (Electron-sea model)
- The metallic radius is one half of the internuclear distance between the 2 adjacent metal ions in the metallic crystal.
- It is longer than the covalent radius.
Comparisons of types of radii of atoms
Van der Waals radius > metallic radius > covalent radius
Van der Waals radius is the largest radii amongst all.
In case of non-metals, atomic radius refers to either covalent or Van der Waal’s radius.
In the upcoming post we will discuss how the atomic radii varies in the group and period.
Check out the post on how to predict the position of the element here :
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