Co-ordinate Bond – Definition, Examples, Formation
In the formation of a covalent bond, both the combining atoms contribute one electron each and the these electrons are mutually shared among them. However, in certain bond formation, one of the combining atoms donates a pair of electrons i.e. two electrons which are necessary for the covalent bond formation, and these electrons are shared by both the combining atoms.
These type of bonds are called coordinate covalent bond or coordinate bond. The combining atom which donates the pair of electron is called a donor atom and the other atom an acceptor atom. This bond is denoted by an arrow starting from the donor atom pointing towards the acceptor atom. (Later in coordination compound, we will refer the donor atom as ligand and the acceptor atom as central-metal atom/ion.
For Example, in ferrocyanide ion [Fe(CN)6]4-, each cyanide ion (CN–) donates a pair of electrons to form a coordinate bond with iron (Fe2+) and these electrons are shared by Fe2+ and CN–.
In certain cases, molecules having a lone pair of electrons such as ammonia donates its pair to an electron deficient molecules such as BF3 to form a coordinate.
In a coordinate covalent bond, one element transfer the electron pair to another element to make a bond. It is represented by the ‘→’ symbol. The head of the arrow represents the acceptor species and tail of the arrow represents the donor species. Example H3N : + H + → [H3N → H]+
Coordinate Covalent Bond:
A covalent bond in which one of the atoms contributes both of the electrons in the shared pair.
A coordinate bond (also called a dative covalent bond) is a covalent bond (a shared pair of electrons) in which both electrons come from the same atom. A covalent bond is formed by two atoms sharing a pair of electrons. The atoms are held together because the electron pair is attracted by both of the nuclei.
Coordinate covalent bonds have one species donate both electrons to the forming the bond while usually covalent bonds have one electron come from each atom.
That is why Al is a good conductor of electricity. It transfers the three outermost electrons very easily to strongly electronegative elements like halogens. However, AlCl3 is not totally ionic, the bonds between Al and Cl are coordinate bond and it has trigonal planar structure (gas phase).
A coordinate covalent bond, also known as a dative bond, dipolar bond, or coordinate bond is a kind of two center, two-electron covalent bond in which the two electrons derive from the same atom. The bonding of metal ions to ligands involves this kind of interaction. This type of interaction is central to Lewis theory.
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