Electron Configurations Chapter 5

Heisenberg Uncertainty Principle 1927 – German Physicist Werner Heisenberg States that it is nearly impossible to know for sure the exact location and the precise velocity of a subatomic particle at the same time

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

Schrödinger ●Treated electrons as waves ● developed a complex mathematical formula to identify the position of an electron

Wave Mechanical Model Quantum Mechanical Model Quantum Mechanical Model Mathematical model – based on probability Mathematical model – based on probability Predicts energy levels for an atom that can be pictured like Bohr’s orbits Predicts energy levels for an atom that can be pictured like Bohr’s orbits Only the PROBABILITY of finding an electron in a certain region of the atom is known Only the PROBABILITY of finding an electron in a certain region of the atom is known

Energy Levels The largest area where electrons can be found (state) The largest area where electrons can be found (state) Maximum of 7 PELs Maximum of 7 PELs Each PEL has one or more sublevels in it Each PEL has one or more sublevels in it

Sublevels Smaller areas within an Energy Level (“city”) Smaller areas within an Energy Level (“city”) # of sublevels in a PEL = PEL # # of sublevels in a PEL = PEL # 4 types of sublevels 4 types of sublevels s p d f

Sublevels PEL# of sublevelstype of sublevel PEL# of sublevelstype of sublevel 11s 22s,p 33s,p,d 44s,p,d,f 55s,p,d,f…

Orbital Region within a sublevel where electrons can be found Region within a sublevel where electrons can be found Sublevel# of orbitals s1 p3 d5 f7

Principles Pauli Exclusion Principle – A maximum of 2 e - can occupy an orbital Pauli Exclusion Principle – A maximum of 2 e - can occupy an orbital Aufbau Principle – Each e - enters an orbital of the lowest energy level first Aufbau Principle – Each e - enters an orbital of the lowest energy level first Hund’s Rule – before a second e - can be placed in any orbital, all the orbitals of that sublevel must contain at least one e - Hund’s Rule – before a second e - can be placed in any orbital, all the orbitals of that sublevel must contain at least one e -

Orbital Diagrams Visual representation of how e - are placed in orbitals Visual representation of how e - are placed in orbitals In an orbital e - have opposite spins In an orbital e - have opposite spins Electrons are represented by arrows Electrons are represented by arrows

Aufbau Diagram

Electron Configurations The “address” of where e - can be found The “address” of where e - can be found Notation tells us the PEL, type of sublevel and the # of e - in that sublevel Notation tells us the PEL, type of sublevel and the # of e - in that sublevel Ex: 1s 2 2s 2 2p 4 Ex: 1s 2 2s 2 2p 4

Valence Valence Energy Levels – outermost energy level of an atom where electrons can be found Valence Electrons – electrons found in the valence energy level - maximum of 8 valence e -

Dot Diagrams