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What is "COORDINATE BOND" ?

A co-ordinate bond formed between two species by sharing of an electron pair where shared pair electron is given by one but shared by both.

ILLUSTRATIVE EXAMPLE (1):
ILLUSTRATIVE EXAMPLE (1):
ILLUSTRATIVE EXAMPLE (1):
ILLUSTRATIVE EXAMPLE (1):
ILLUSTRATIVE EXAMPLE (1):

CONCLUSIONS:
(1)  Atoms of second period elements follow octed rule in doing so either they accept co-ordinate bond or they form co-ordinate bond.  However atoms of 3rd period elements perfectly form double bond (pi bond) in the place of co-ordinate bond if direction of co-ordinate bond is from centre to substituent.
(2) If maximum covalency rule applied and pi bonds have formed then back bond is not considered in species
For example H2SO4 and HClO4  have no back bond there is double bond. 

What is synergic bonding 

Related Questions:

Why all the tetrahedral Complexes are high spin Complexes?

Why Fe(CO)₅ is colourless while Fe(bipy)(CO)₃ is intensely purple in colour ?

Why [Mn(H₂O)₆]⁺² is colourless although in which Mn⁺² ion had five unpaired electrons ?

Why [FeF₆]^3– is colourless whereas [CoF₆]^3– is coloured? 

Why [Ni(CN)₄]^-2 is colourless while [Ni(H₂O)₄]^-2 is colour although both have +2 oxidation state and 3d⁸ configuration ?

Classification of oxides on basis of oxygen content:

(1) Normal Oxides:

(2) Sesqui Oxides:

(3) Mixed Oxides:

(4) Peroxides:

(5) Super Oxides:

(6) Suboxides:

(7) Perovskites:

(8) Spinel Oxides:

(9) Cage like Oxide:

(1) Normal oxides:

The Oxides in which oxidation state of central atom is found to be one of the it's common oxidation state. The are also called acid anhydride because on dissolving them  into water oxygen acid is formed in which oxidation state of central atom is found to be same as present in Oxide.

examples:  B₂O₃, CO₂, N₂O₃, N₂O₅, SO₂, SO₃, Cl₂O₇, XeO₃, XeO₄ etc.

(2) Sesqui oxides:

The oxides in which number of oxygen atoms pet central atoms is found to be 3/2 .And it may be ionic, covalent or missed oxides.Mostly M₂O₃ type Oxides (Corundum structure) are sesqui Oxides.  Where M⁺²= Al, Ga, Ti, V, Cr, Fe, The etc.

Examples , B₂O₃, N₂O₃, Al₂O₃ ( covalent oxide) Fe₂O₃ (ionic oxide) Pb₂O₃ (mixed oxide)
(3) Mixed Oxides:

The oxides in which oxidation state of oxygen atom is found to be it's uncommon oxidation state on central atom. Mixed oxides on dissolving in water undergo "disproportionation" 

For examples B₂O₃, ClO₂, Cl₂O₇ etc.
(4) Peroxides:

The oxides in which  calculated oxidation state of central atom is more than maximum oxidation state of central atom due to the presence of peroxide linkage.

For examples, H₂O₂, Na₂O₂, BaO₂, PbO₂, CrO₅ etc.
(5) Super Oxides:

The oxides in which oxidati state of oxygen atom always -1/2, and super oxides are always ionic and paramagnetic.

For examples KO₂ , PbO₂, (NH₄)O₂ etc.

KO₂ => k+[O-O]-. Have following character

Bond pair -2

Lone pair -2

Hybri- sp2, linear non planner and bond angle not applicable.

(6) Suboxides:

The oxides contains more oxygen atoms as compare to central atoms and according to valency requirements of central atoms number of oxygen atoms are not sufficient.

For examples B₂O₃, C₃O₂, C₁₂O₉, Pb₃O, Rb₉O₂, Cs₁₁O₃ etc. 

(7) Perovskite oxides:

ABO₃ type Oxides are also called Perovskite for examples CaTiO₃  And BaTiO₃.

(8) Spinel Oxide:

(7) Case Oxides:

 P₄, P₄O₄, P₄O₁₀, P₄S₃, P₄S₁₀, N₄(CH₂)₆

_{Structure of P4O6 and P4O10}