Title Covalent Best Explained- MOT cont...pdf ✅

© 2020, BYJU'S. All rights reserved 01 CHEMICAL BONDING COVALENT BEST EXPLAINED - MOT CONTINUED... CHEMISTRY NOTES What you already know • Molecular orbital theory (MOT) • Colour of a molecule • Magnetic properties • Existence of a molecule • Bond order Recap Features of MOT Types of MOs Antibonding molecular orbitals (ABMO) • Electrons are associated with the molecule as a whole and not with the individual atoms. • The atomic orbitals (AOs) of individual atoms combine to form the molecular orbitals (MOs). • The energies of AOs of the combining atoms must be comparable. • AOs are monocentric, while MOs are polycentric. • Two AOs produce two MOs, one with a lower energy and the other with a higher energy than the energy of combining AOs. • Number of MOs = Number of AOs involved in combination • The molecular orbitals like atomic orbitals are filled in accordance with the Aufbau principle obeying the Pauli's exclusion principle and the Hund's rule of maximum multiplicity and the relative energies of orbitals. • There are two types of molecular orbitals. They are as follows: ABMO (Antibonding molecular orbital) and BMO (Bonding molecular orbital) • Linear combination of atomic orbitals • Electron configuration according to MOT • Highest occupied molecular orbital (HOMO) • Lowest unoccupied molecular orbital (LUMO) • Limitations of molecular orbital theory Bonding molecular orbitals (BMO) What you will learn
© 2020, BYJU'S. All rights reserved 02 Fig. 1: Molecular orbital energy diagram Fig. 2: Constructive interference of waves Fig. 3: Electron probability density in BMO H H Energy σ*1s σ1s 1s 1. BMO: They are formed by the additive combination of the atomic orbital wave functions so that the amplitude of the new wave is given by, ΨBMO = ΨA + ΨB • They are formed by constructive interference. • They are lower in energy than a pure atomic orbital. • They stabilise the molecule. • The electron density increases in the internuclear region. • They may or may not have a nodal plane. • They are represented by σ and π. Examples: σ1s, σ2pz , π2px , π2py . 1s LCAO (Linear combination of atomic orbitals) Wave x Wave y Wave z Ψ2 AO MO AO
© 2020, BYJU'S. All rights reserved 03 2. ABMO: They are formed by the subtractive combination of the atomic orbital wave functions. The amplitude of the new wave is given by, ΨABMO = ΨA - Ψ B • They are formed by destructive interference. • They are higher in energy than a pure atomic orbital. • They destabilise the molecules. • The electron density decreases in the internuclear region. • They always have a nodal plane. • They are represented by σ* and π*. Examples: σ*1s, σ*2pz , π*2px , π*2py . Wave x Wave y Wave z Fig. 4: Destructive interference of waves Fig. 5: Electron probability density in ABMO H H Ψ2 Properties Explained Using Molecular Orbital Theory: MOT Molecular orbital electronic configuration Existence of a molecule Bond order Bond stability Colour Magnetic behaviour Bond length BOARDS NEET