In Co-ordinate bond, the acceptor atoms must essentially contain in its valency shell an orbital:
Understanding the Acceptor Atom in a Coordinate Bond
A coordinate bond, also known as a dative bond, is a type of covalent bond where one atom provides both the shared electrons. This differs from a typical covalent bond where each atom contributes one electron to the shared pair.
In the formation of a coordinate bond, we have two key participants:
- Donor Atom: This atom possesses a lone pair of electrons (a pair of non-bonding electrons) that it can donate.
- Acceptor Atom: This atom must be able to accept the lone pair of electrons donated by the donor atom.
Requirement for the Acceptor Atom's Valence Shell Orbital
For the acceptor atom to accept a pair of electrons, it must have a suitable space available in its valence shell. This space is an orbital that can accommodate the incoming electron pair. Let's consider what kind of orbital is needed:
- An orbital already containing electrons (either singly or paired) cannot accept an additional pair of electrons according to the Pauli Exclusion Principle (which states that no two electrons in an atom can have the same set of four quantum numbers, meaning an orbital can hold a maximum of two electrons with opposite spins).
- Therefore, to accept a lone pair, the acceptor atom must have an orbital that is available and can house two electrons. This means the orbital must be empty.
Let's evaluate the given options based on this understanding:
| Option | Description of Orbital | Suitability for Accepting a Lone Pair |
|---|---|---|
| 1 | With single electron | Not suitable. A single electron in an orbital means it's half-filled. It could potentially form a regular covalent bond or accept one more electron to become paired, but it cannot readily accept a full lone pair (two electrons) into that already occupied orbital. |
| 2 | With no electron | Suitable. This describes an empty orbital. An empty orbital can readily accept a lone pair of electrons donated by another atom to form a coordinate bond. |
| 3 | With three electrons | Not suitable. An orbital can hold a maximum of two electrons. An orbital with three electrons is not a standard configuration and violates basic orbital filling principles. |
| 4 | With paired electron | Not suitable. An orbital with a paired electron is already full (contains two electrons). It cannot accept another pair of electrons. |
Based on the principles of chemical bonding and orbital occupancy, the acceptor atom in a coordinate bond must possess an empty valence shell orbital to receive the lone pair of electrons from the donor atom.
For example, in the formation of the ammonium ion ($\text{NH}_4^+$) from ammonia ($\text{NH}_3$) and a proton ($\text{H}^+$):
- Ammonia ($\text{NH}_3$) acts as the donor, as nitrogen has a lone pair of electrons.
- The proton ($\text{H}^+$) acts as the acceptor. A proton is essentially a hydrogen nucleus with no electrons. Its valence shell (the first shell) had 1 electron in a neutral hydrogen atom ($\text{1s}^1$). When it loses this electron to become $\text{H}^+$, its $\text{1s}$ orbital becomes empty ($\text{1s}^0$). This empty $\text{1s}$ orbital can accept the lone pair from the nitrogen atom in ammonia.
Therefore, the presence of an empty orbital in the acceptor atom is essential for coordinate bond formation.
Important Questions from Chemical Bonding
The element having which of the following electronic configuration will have highest ionization energy?
Which of the following is true about interhalogen compounds?
The shape of the molecule depends on the _______
The geometrical shape of PCl5 molecules is
Which of the following molecules has T-shaped geometry?
