Different type of radius in atoms

COVALENT RADIUS:-   covalent radius is half of the internuclear  separation between the nuclie of two single - bonded atoms of the same species. 

d = internuclear distance b/w two nuclie

                 

                  r(covalent  radius)  = d/2

- covalent radius are two types:-

1. Homoatomic covalent radius:- 
2. Heteroatomic covalent radius:-

Homoatomic covalent radius:- When two same atoms combined together and form covalent bond. 

Generally taken as half of the bond length of homoatomic covalent molecules(where identical atoms are bonded together.) 

:.for example :- when two hydrogen atom(H) combine ,their covalent radius is half of the two hydrogen atom internucleus distance. 

r(H-H) = d(H-H)/2

 Heteroatomic  covalent radius :- When two different species(A-B) combine together. 

 Based on electronegativity  heteroatomic covalent radius are two types:-

1. If E.N. of atom is same :- 

For example :- H-H ,N-Cl

    2. If E.N. of atom is different :-

 For example :- H-Cl

 Calculation of heteroatomic  covalent radius (when E.N. is different)

 

• IONIC RADIUS :-   The ionic radius is the distance between the nucleus and the electron  in the outermost shell of an ion. 
• It is the radius of an monoatomic ion in an ionic crystal structure. 
• Ion may be larger or small than the neutral atom. 
• When an atom loses an electron to form a cation, the other electrons are more attracted to the nucleus and the radius of the ion gets smaller. 
• Similarly  ,when an electron is added to an atom, forming an anion, the added electron increases the size of the electron  cloud by interelectonic repulsion.

For example:- 

Atomic radius of different atoms:--

                Li = 134

                O = 73

                 F = 71

                 Na =154

Ionic radius of different  atoms :---

   

               Li+ = 90

               O²- =126

                F- = 119

                Na+ = 116

:-- all above data mention in picometer (pm)  

• METALLIC RADIUS :-   The metallic radius is half of the total distance between the nuclei of two adjacent atoms in a metallic cluster.

             r(metallic radius)  = d(A-A)/2

    

• VANDERWALL  RADIUS :-   Vanderwall radius is the equal to one half the distance between two unbonded atoms when the electrostatic forces between them are balanced. 

      r(v.w.) = d(H2H2)/2

• BOH'R  RADIUS :--  Applicable on monoelectronic  species.

For eg. :- H , He+ , Li2+

:. Formula for calculation of bohr radius :--

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