Electron ConfigurationsElectron Configurations

Chapter 5Chapter 5

Heisenberg Uncertainty Heisenberg Uncertainty PrinciplePrinciple

1927 – German Physicist Werner Heisenberg1927 – German Physicist Werner Heisenberg

States that it is nearly impossible to States that it is nearly impossible to know for sure the exact location and know for sure the exact location and the precise velocity of a subatomic the precise velocity of a subatomic particle at the same timeparticle at the same time

ExplanationExplanation

To “see” an electron, we pass photons To “see” an electron, we pass photons through it (light is deflected back) through it (light is deflected back) but we can’t know it’s true velocity but we can’t know it’s true velocity since when the photons hit it, the since when the photons hit it, the velocity changesvelocity changes

SchrödingerSchrödinger

●●Treated electrons as wavesTreated electrons as waves

● ● developed a complex mathematical developed a complex mathematical formula to identify the position of an formula to identify the position of an electronelectron

Wave Mechanical ModelWave Mechanical Model

Quantum Mechanical ModelQuantum Mechanical Model

Mathematical model – based on probabilityMathematical model – based on probability

Predicts energy levels for an atom that can Predicts energy levels for an atom that can be pictured like Bohr’s orbitsbe pictured like Bohr’s orbits

Only the PROBABILITY of finding an electron Only the PROBABILITY of finding an electron in a certain region of the atom is knownin a certain region of the atom is known

Energy LevelsEnergy Levels

The largest area where electrons can The largest area where electrons can be found (state)be found (state)

Maximum of 7 PELsMaximum of 7 PELs

Each PEL has one or more sublevels Each PEL has one or more sublevels in itin it

SublevelsSublevels

Smaller areas within an Energy Level Smaller areas within an Energy Level (“city”)(“city”)

# of sublevels in a PEL = PEL ## of sublevels in a PEL = PEL #

4 types of sublevels4 types of sublevels ss pp dd ff

SublevelsSublevels

PELPEL # of sublevels# of sublevels type of type of sublevelsublevel

11 11 ss

22 22 s,ps,p

33 33 s,p,ds,p,d

44 44 s,p,d,fs,p,d,f

55 55 s,p,d,f…s,p,d,f…

OrbitalOrbital

Region within a sublevel where electrons Region within a sublevel where electrons can be foundcan be found

SublevelSublevel # of orbitals# of orbitals

ss 11

pp 33

dd 55

ff 77

PrinciplesPrinciples

Pauli Exclusion PrinciplePauli Exclusion Principle – A maximum – A maximum of 2 eof 2 e-- can occupy an orbital can occupy an orbital

Aufbau PrincipleAufbau Principle – Each e – Each e-- enters an enters an orbital of the lowest energy level firstorbital of the lowest energy level first

Hund’s RuleHund’s Rule – before a second e – before a second e-- can be can be placed in any orbital, all the orbitals of placed in any orbital, all the orbitals of that sublevel must contain at least one that sublevel must contain at least one ee--

Orbital DiagramsOrbital Diagrams

Visual representation of how eVisual representation of how e-- are are placed in orbitalsplaced in orbitals

In an orbital eIn an orbital e-- have opposite spins have opposite spins

Electrons are represented by arrowsElectrons are represented by arrows

Aufbau DiagramAufbau Diagram

Electron ConfigurationsElectron Configurations

The “address” of where eThe “address” of where e-- can be can be foundfound

Notation tells us the PEL, type of Notation tells us the PEL, type of sublevel and the # of esublevel and the # of e-- in that in that sublevelsublevelEx: 1sEx: 1s222s2s222p2p44

ValenceValence

Valence Energy LevelsValence Energy Levels – outermost – outermost energy level of an atom where energy level of an atom where electrons can be foundelectrons can be found

Valence ElectronsValence Electrons – electrons found in – electrons found in the valence energy levelthe valence energy level

- maximum of 8 valence e- maximum of 8 valence e--

Dot DiagramsDot Diagrams