Inorganic Chemistry: Atomic Orbitals

Basics of Atomic Orbitals

The space around an atomic nucleus where there’s a high probability of finding an electron is called an atomic orbital.
Each orbital can hold two electrons with opposite spins. The Pauli Exclusion Principle restricts any more than two electrons being in one orbital.
The shape of the orbital is determined by the angular momentum quantum number, often known as the “orbital shape quantum number.”

Types of Atomic Orbitals

There are four types of atomic orbitals: s,p,d, and f.
The s orbital is spherical in shape and has only one subshell.
The p orbital has a dumbbell shape and contains three degenerate p orbitals (px, py, pz) each of which can hold two electrons.
The d orbital has a more complex shape and there are five d orbitals in each d subshell.
The f orbital has an even more complex shape, with seven f orbitals in each f subshell.

Quantum Numbers and Atomic Orbitals

Each atomic orbital is uniquely defined by a set of quantum numbers: principal quantum number (n), angular momentum quantum number (l), and magnetic quantum number (ml).
The principal quantum number (n) defines the energy level or shell in which the orbital lies.
The angular momentum quantum number (l) defines the shape of the orbital. When l=0, it’s an s orbital; l=1, it’s a p orbital; l=2, it’s a d orbital, and l=3, it’s an f orbital.
The magnetic quantum number (ml) defines the orientation of the orbital in space.

Electron Configuration and Atomic Orbitals

Electron configuration describes how electrons are distributed in an atom’s atomic orbitals.
Electrons populate atomic orbitals in a manner to achieve the lowest energy state, following the Aufbau Principle. They fill each orbital singly before doubling up, as described by Hund’s Rule.
The Pauli Exclusion Principle states that no two electrons in an atom can have the exact same set of four quantum numbers, effectively limiting an atomic orbital to two electrons maximally.

Atomic Orbitals and Chemical Bonding

Overlap of atomic orbitals leads to the formation of chemical bonds.
An ionic bond is formed by the transfer of electrons from one atom to another, and a covalent bond involves the sharing of electrons between atoms.
Hybridisation of atomic orbitals allows for the creation of equivalent bonding orbitals in molecules, explaining molecular shapes and bond angles.

Atomic Orbitals and Spectroscopy

Excitation of electrons in atoms can cause them to move from their ground state to an upper level, which corresponds to an energy difference matching the energy of absorbed light or other electromagnetic radiation.
Such atomic electron transitions can be detected and analysed using different spectroscopic techniques, providing valuable information about the atom’s electronic structure and environment.