CHAPTER 6 ELECTRONIC STRUCTURE OF THE ATOM

COULOMB’S LAW (POTENTIAL ENERGY FORM)

REVIEW OF ELECTROMAGNETIC RADIATION c = λν λ is wavelength (in meters) ν is frequency (in s -1 ) c is speed (in m/s) for light, c = 3.00 x10 8 E = hν h is Planck’s Constant (6.626 x J· s)

LIGHT EMISSIONS OF SOLIDS

LIGHT EMISSION OF HYDROGEN GAS

BOHR’S HYDROGEN ATOM Light is absorbed or emitted from electrons transitioning between energy levels. Since only certain energies are observed, only certain energy levels can exist. This is called quantization of energy levels. Think of a ladder instead of a ramp.

ABSORPTION AND EMISSION

ENERGY LEVELS OF HYDROGEN

MATTER WAVES All matter has both particle and wave properties (wave/particle duality). Large objects moving slowly produce waves that are too small to observe. For small objects moving quickly (like electrons), wave properties are important.

WAVE NATURE OF ELECTRONS

HEISENBERG UNCERTAINTY PRINCIPLE

SCHRODINGER MODEL OF H Electrons act as standing waves Only certain wave functions are “allowed” Wave behavior is described by a wave function, Ψ. Ψ 2 describes the probability of finding the electron in a certain location. Also called the electron density

ORBITALS Each wave function describes the shape the electron cloud can take. These shapes are called orbitals. We organize orbitals by shells and subshells Shells define size and energy (n = 1, 2, 3…) Subshells define shape (s, p, d, f) Each subshell has a different number of orbitals s = 1 orbital p = 3 orbitals d = 5 orbitals f = 7 orbitals

SHAPES OF ORBITALS

ENERGIES OF ORBITALS Single electron atoms Multi electron atoms Why?

ELECTRON SPIN Electrons exhibit a magnetic field They don’t actually spin, but we think of them as spinning. They can only spin two ways. For sake of argument, we’ll call it up and down. Allowed spins: + ½ and – ½.

SPIN AND MAGNETISM Paramagnetic: unpaired electrons will align in presence of a real magnet. Ferromagnetic (real magnets): unpaired electrons aligned in the same direction. diamagnetic paramagnetic ferromagnetic

ELECTRON CONFIGURATIONS A listing of how many electrons occupy each orbital. 3 Rules Aufbau Principle – Electrons fill lowest energy orbitals first. Pauli Exclusion Principle – Each orbital can hold two electrons if they have opposing spins. Hund’s Rule – Each subshell is filled in a way to give the maximum number of unpaired electrons (maximum degeneracy).

THREE DIFFERENT NOTATIONS Electron Configuration List subshells and how many electrons they contain. 1s 2 2s 2 2p 6 3s 1 Noble Gas Notation [Ne]3s 1 where [Ne] = 1s 2 2s 2 2p 6.

PERIODIC BLOCKS