Bond characterstics

in this lesson, I mention bond characteristics.in bond characteristics we divide it into three parts the first one is the bond length, then bond energy and the third one is about the bond angle, how and why they are formed this important and basic topic.

1. BOND CHARACTERSTICS LESSON 3 PART-1

2. TOPICS WE HAVE TO COVER IN BOND CHARACTERSTICS PART -1: BOND LENGTH 2)BOND ANGLE 3)BOND ENTHAPLY

3. BOND LENTH It is the equilibrium distance between two bonded atoms in a molecule . Each atom of the bonded pair contributes equal to the bond length. It is expressed in terms of angstrom(A*) or picometer (pm). Similarly , in a covalent compound , bond length is obtained by adding up the covalent radii of two bonded atoms. The covalent radius is half of the distance between two similar atoms joined by a covalent bond in the same molecule.

4. VANDEWAAL RADII The half of the bond length between two non- bonded atoms hold together by vander waal force of attraction.

5. SOME POINTS REGARDING BOND PARAMETERS: Triple bonds are considered to be the strongest bonds followed by double and single bonds and as we know, bond length decreases as the bond strength increases (due to increased attractions or due to formation of more bonds) The bond length of the homonuclear diatomic molecules are twice the covalent radii.  

6. (3) BOND ENTHAPLY It is defined as amount of energy required to break one mole of bonds of a particular type between two atoms in gaseous state. The unit of bond of enthalpy is in KJ/mol. Stronger the bond larger bond enthalpy we required.

7. SOME POINTS REGARDING BOND strength: ( 1) Strength of sigma bond is more than pi bond. Resonance in the molecule affect the bond energy . (3)Bond energy decreases down the group in case of similar molecules (4)Bond energy increase in the following order: s < p < sp < sp2 < sp3 (5)Bond energy decresae with the increase in the number of lone pair. C – C > N – N > O – O (No lone pair) (One lone pair) (Two lone pair)

8. (2) BOND ANGLE It is defined as the angle between the orbitals containing bonding electron pairs around the central molecule . It help us in determining it’s shape. For example H-O-H bond angle in water can be represented as

9. (1) Lone pair repulsion: Bond angle is affected by the presence of lone pair of electrons at the central atom. A lone pair of electrons at the central atom always tries to repel the shared pair (bonded pair) of electrons. Due to this, the bonds are displaced slightly inside resulting in a decrease of bond angle. (2) If the electronegativity of the central atom decreases, bond angle decreases. (3) Hybridization: Bond angle depends on the state of hybridization of the central atom Hybridization:  sp3 , Bond angle:  109∘29 Example:  CH4 Hybridization:  sp2 , Bond angle:  120∘ , Example:  BCl3 Hybridization:  sp, Bond angle:  180∘ , Example:  BeCl2 Generally s- character increase in the hybrid bond, the bond angle increases

10. Relation between bond order, bond length, bond enthalpy