Concept of Back Bonding

In which of the following cases, the strength of back bonding is maximum

What is LCAO method? How does it lead to the concept of bonding and antibonding molecular orbitals? What are the main points of difference between bonding and antibonding molecular orbitals?

The molecule , which are electron deficient having tendency to form back bonding, in which transfer of lone pair of electron from filled orbital of an atom to the vacant orbital of the adjacent atom. While some electron deficient species which are not capable to form back bonding, then driving forces occurs for dimerisation/polymerisation to achieve octet temporily or permanently by the monomeric species. which of the following species is most acidic and have NO back bonding ?

The molecule , which are electron deficient having tendency to form back bonding, in which transfer of lone pair of electron from filled orbital of an atom to the vacant orbital of the adjacent atom. While some electron deficient species which are not capable to form back bonding, then driving forces occurs for dimerisation/polymerisation to achieve octet temporily or permanently by the monomeric species. Which of the following matching is INCORRECT between molecule and the orbitals of atoms involved in bridge bond.

Concept of Acids and Bases

Statement-1 : PH_(3) and PF_(3) are pyramidal in shape with one lone pair on P . But PF_(3) has greatest bond angle than PH_(3) . and Statement-2 : Back bonding is present in PF_(3) but absent in PH_(3) .

Which of the following molecule is planar due to back bonding

In which of the following compounds , back bonding is possible

Which of the following statement is true on the basis of back bonding.?

In which of the following compounds observed bond angle is found to be greater than expected, but not due to back bonding.