1. Backbonding Backbonding is a type of resonance. Back bonding increases stability. It does affect properties of molecules, like Hybridisation & Dipole moment. In Π back bonding, the electrons move from an atomic orbital on one atom to a π* anti-bonding orbital on another atom or ligand.

2. pπ-pπ bonding P - Pi p - Pi bond is formed when one p orbital of each combining atom is overlapped laterally. P - Pi d - Pi bond is formed when p orbital of one atom and d orbital of another atom overlap laterally.

3. dπ-pπ back bonding In this electrons are donated from filled d- orbitals of the metal to the empty d-orbitals of the ligand. pπ– pπ bonding: In this type of bonding p-orbital of one atom overlap sideways with p-orbital of another atom which results in the formation of π-bond, known as pπ– pπ bond.

5. BI3>BBr3>BCl3>BF3.this trend is due to pie back bonding. All halides have lone pairs, they donate one lone pair to boron by overlapping with the p orbital of boron. Effective overlap between orbital’s decreases due to large size of p orbital of halides.Hence,electron deficiency of boron atom in its halides follow the trend--BI3>,BBr3,>BCL3>BF3 and so it is the Lewis acidity ORDER. A species which is more electron deficient will electron easily and hence will be more acidic.

10. A stress on metal-carbonyl bond

11. MO diagram of CO

14. Alkene with metals