Lecture 2.0 Bonds Between Atoms Famous Physicists’ Lecture

Electronic Structure in Atoms Max Planck –Electron (1897) has duality, Wave E=hc/λ = h, –λ =wavelength of electron – =frequency Particle of mass, m e

Only specific orbits = Atomic Orbitals –Circumference of orbit = n*λ –for Hydrogen, Z=1, R 1 = nm –Z= number of protons Bohr Atom

Electronic Structure in Atoms Ionization energy = transition from n   Emission Radiation (Light and X-rays) –transition n a  n b gives off Photon with energy Bonding in Molecules – Ionic and Covalent Louis Victor Pierre Raymond duc de Broglie

E N Not correct due to charge screening and QM

Emission Line Spectra

Energy Level Diagrams, Hydrogen 1 K eV eV eV L eV

Periodic Table of Element Chemical Properties

Heisenberg Uncertainty Principle  (m e v)  x  h/(2π) Cannot specify both momentum (or velocity) and location of an electron at same time Electrons are smeared in space Probability of finding an electron at a location is best way to describe and electron

Schrodinger Wave Equation (time independent) Wave Function, ψ=f(r,θ,φ) Probability of finding an electron= | ψ| 2 = ψ* ψi.e. complex conjugate

Pauli’s Exclusion Principle - Only one electron in each location accounting for spin Principle Q#Orbital Q#Magnetic Q# Spin Q#

Zeeman Effect = Splitting or emission lines if in B field

Shape of Orbitals

Bonding in Molecules Ionic - electrons stolen Covalent - electrons shared –Metal –hybridization, sp, sp 2, sp 3 Molecular Orbitals for shared electrons = covalent bonds

Atoms in Solids Ionic Bonding, NaCl Covalent Bonding Metals Hetero Atoms = Ceramics, e.g. MgO

Electrostatic forces in Ionic Solids Many Atoms at various separations –Maudelin Constant, M d –NaCl, a o =0.281 nm and E latttice =8.95 eV.

Repulsive Force at small r Total Force = Coulomb Force + Repulsive Force

Metallic Bonding Electrons Free to move among all atoms –Electron Gas Determines –Electrical Conduction –Thermal Conduction

In Covalent Crystalline Solids, what happens to the atomic orbitals?

Molecular Orbitals New Energy –Bonding –Anti Bonding New Shapes to Orbitals if hybridization 1s

Bonds Between Molecules Hydrogen Bonding Van der Waals Forces –Dipole-Dipole interactions Dipole Moment = Charge * separation –Permanent –Instantaneous

Melting Point Molecular Solids Metals Ionic Solids Covalent Solids Strength of Inter-Molecular Bonds Melting Point