NO3-

Overview:
NO3- is the chemical formula for nitrate ion, which consists of one nitrogen atom bonded to three oxygen atoms. It has a trigonal planar molecular geometry with a -1 charge. Nitrate is a polyatomic ion that is commonly found in chemical compounds and is important in various biological and environmental processes.

Electron Configuration:
To understand the pi and sigma bonds in NO3-, it is essential to examine the electron configuration of the atoms involved. Nitrogen (N) has an electron configuration of 1s2 2s2 2p3, while each oxygen (O) atom has an electron configuration of 1s2 2s2 2p4.

Sigma Bond:
A sigma bond (σ bond) is formed when two atomic orbitals overlap end-to-end, allowing the electron density to be concentrated between the two nuclei. In NO3-, each oxygen atom forms a sigma bond with the nitrogen atom. This results in the formation of three sigma bonds in NO3-, with each oxygen atom sharing one electron with the nitrogen atom.

Pi Bond:
A pi bond (π bond) is formed when two p orbitals overlap sideways, resulting in the sharing of electron density above and below the internuclear axis. In NO3-, there is a pi bond between the nitrogen and each oxygen atom. However, due to the trigonal planar geometry of NO3-, the p orbitals of nitrogen and oxygen atoms are not parallel, making the pi bond weaker compared to a typical double bond.

Pi-D Pi Bond:
The pi-d pi bond is a type of pi bond formed by overlap between a p orbital and a d orbital. In NO3-, the nitrogen atom has one unhybridized 2p orbital and one empty 2p orbital. Additionally, it has one unhybridized 2s orbital and three hybridized 2p orbitals involved in sigma bonding. The empty 2p orbital of nitrogen can interact with a d orbital of an oxygen atom to form a pi-d pi bond.

Conclusion:
In summary, NO3- has a total of three sigma bonds and three pi bonds. The sigma bonds are formed by the overlap between the sp2 hybridized orbitals of nitrogen and the 2p orbitals of the oxygen atoms. The pi bonds are formed by the sideways overlap of the p orbitals between nitrogen and each oxygen atom. Additionally, the nitrogen atom can form a pi-d pi bond with the d orbital of an oxygen atom. Understanding the bonding in NO3- is crucial in comprehending its chemical reactivity and properties.