Saved Bookmarks
| 1. |
Explain covalent radius and ven der Waal's radius. |
|
Answer» Solution :Covalent radius : Each atom of the bonded pair contributes to the bond length. (see figure) Covalent radius of atom : In case of covalent bond the contribution from each atom is called the covalent radius of that atom. Covalent radius : The covalent radius is measured approximately so the radius of an atom.s core which is in contact with the core of an adjacent atom in a bonded situation. The covalent radius is HALF of the distance between two similar atoms joined by a covalent bond in the same molecule. e.g. : The distance between two atom of `Cl_(2)` molecule is 1.98 pm. The covalent radius value of Cl is 1.98 + 2 = 0.99 pm. Bond length of bond between two different atom: AB is covalent molecule `therefore ` Covalent radii of A atom = `r_(A)` `therefore`Covalent radii of B atom = `r_(B)` . `therefore ` Bond length of AB is R = `r_(A) + r_(B)` This given is following figure.  van der Waals radii : The van der Waals radius represents the overall SIZE of the atom which incudes its valence shell in a nonbonded situation. The van der Waals radius is half of the distance between two similar atoms in separate molecules in a solid. The convent and van der Waals radius in chlorine molecule are in following figure  Where, `r_(c) ` = Covalent radii = `("Distance between centre of two Cl ")/(2) ` = `(198 pm)/(2) ` = 99 pm `r_(vdw)`= van der Waals radius `= ("Dist. betn. the int. nuclear axis of two" Cl_(2))/(2) ` = `(360 pm)/(2)` = 180 pm Remember : Covalent radius is the one half of distance between two atoms of same molecule while van der Wall radius is the one haff of distance between two different molecule Table - l : Some bond length (In pm)  Orderofbondlength: `O - H lt C - H lt N - O lt C - O ` = ` C - N lt C - C ` e.g. (i) N- O `gt N = O` (ii) C - O `gt ` C = O (iii) C - N `gt` C = N `gt` C = N (iv) `C - C gt C = C gt C = C ` Table - 2 :Halogen (F, Cl, Br, I join with same atom than the order of Bond length ) Af `lt ` ACl `lt `ABr `lt ` Al .  Note-I : In period moving from left to right covalent radius DECREASES. Except F other Halogen Cl, Br, I has max radius. Note-2 : In GROUP as we move down the covalent radius increase. Note: Understand above table, separate and use in deciding order. |
|