Formation of Coordinate Covalent Bond in SO4-2

Introduction:
The sulfate ion (SO4-2) is a polyatomic ion that consists of one sulfur atom bonded to four oxygen atoms. The formation of a coordinate covalent bond in SO4-2 can be explained by the Lewis dot structure and the concept of electron pair donation.

Lewis Dot Structure of SO4-2:
In the Lewis dot structure of SO4-2, the sulfur atom is located at the center and is surrounded by four oxygen atoms. The sulfur atom has six valence electrons, while each oxygen atom has six valence electrons. Therefore, the total number of valence electrons in SO4-2 is 6 + 4(6) + 2 = 32.

Formation of Coordinate Covalent Bond:
The formation of a coordinate covalent bond in SO4-2 involves the donation of a lone pair of electrons from a Lewis base to an empty orbital of the sulfur atom.

Step 1: Identify the Lewis Base:
In the case of SO4-2, the Lewis base can be any species that possesses a lone pair of electrons. For example, ammonia (NH3) can act as a Lewis base in the formation of a coordinate covalent bond with SO4-2.

Step 2: Donation of Electron Pair:
The lone pair of electrons from the Lewis base (e.g., ammonia) is donated to an empty orbital of the sulfur atom in SO4-2. This donation occurs due to the high electronegativity of oxygen atoms, which makes them strongly attract electrons towards themselves. As a result, the sulfur atom becomes electron-deficient and can accept a lone pair of electrons.

Step 3: Formation of Coordinate Covalent Bond:
The donation of the lone pair of electrons from the Lewis base to the sulfur atom results in the formation of a coordinate covalent bond. In this bond, both electrons are donated by the Lewis base, while the sulfur atom contributes an empty orbital to accommodate the electron pair. The coordinate covalent bond is represented by an arrow pointing from the Lewis base to the sulfur atom.

Conclusion:
In summary, the formation of a coordinate covalent bond in SO4-2 involves the donation of a lone pair of electrons from a Lewis base to an empty orbital of the sulfur atom. This process allows the sulfur atom to complete its octet and stabilize the sulfate ion. The concept of electron pair donation is crucial in understanding the formation of coordinate covalent bonds in polyatomic ions like SO4-2.