Quantum Numbers and Writing Electron Configurations Electrons in Atoms Quantum Numbers and Writing Electron Configurations

Quick Review - Nucleus Nucleus concentrated mass of p+ & n0 held together by the strong force Thomson & Rutherford’s experiments

Quick Review - Electrons The Bohr Model of the Atom electrons orbiting the nucleus much like planets orbiting the sun - WRONG (electrons are more like bees around a hive) Electrons are in certain energy states

Quick Review - Electrons Schrodinger – quantum mechanical model of the atom Atomic orbitals describe the electron’s probable location

Arrangement of Electrons Quantum numbers Specify the “address” of each electron in an atom UPPER LEVEL

Quantum Numbers Principal Quantum Number ( n ) Principle Energy level Size of the orbital

Quantum Numbers f d s p Energy sublevels Shape of the orbital Principle energy level 1 has 1 sublevel, principle energy level 2 has 2 sublevels,… f d s p

Quantum Numbers Within each sublevel you have orbitals

Relative sizes of the spherical 1s, 2s, and 3s orbitals of hydrogen.

The three 2p orbitals.

The shapes and labels of the five 3d orbitals.

Quantum Numbers 2s 2px 2py 2pz Orbitals combine to form a spherical shape. 2s 2pz 2py 2px

Quantum Numbers n = # of sublevels per level n2 = # of orbitals per level

How principal levels can be divided into sublevels.

Principal level 2 shown divided into the 2s and 2p sublevels.

Energy Levels, Sublevels, Orbitals, Electrons Sublevels in main energy level (n sublevels) Number of orbitals per sublevel Electrons per sublevel electrons per level (2n2) 1 s 2 p 3 6 8 d 5 10 18 4 f 7 14 32

Writing Electron Configuration Electrons in Atoms Writing Electron Configuration

Electron Configurations No two electrons in an atom can have the same 4 quantum numbers. Each e- has a unique “address”:  energy level sublevel (s,p,d,f) orbital electron

General Rules Aufbau Principle Electrons fill the lowest energy orbitals first. “Lazy Tenant Rule”

Filling Orbitals

General Rules Pauli Exclusion Principle Each orbital can hold TWO electrons with opposite spins.

General Rules WRONG RIGHT Hund’s Rule Within a sublevel, place one e- per orbital before pairing them. “Empty Bus Seat Rule” WRONG RIGHT

Notation C 1s 2s 2p Orbital Diagrams a box for each orbital An arrow for each electron Label each box with principle quantum number and sublevel Example: orbital diagram for a ground state carbon atom C 1s 2s 2p

Orbital Diagram

Orbital Diagrams

1s2 2s2 2p4 O Notation 1s 2s 2p 8e- Orbital Diagram Electron Configuration 1s2 2s2 2p4

Notation Practice Write the orbital diagrams and electron configurations for the following ground state atoms: Lithium Fluorine

S 16e- 1s2 2s2 2p6 3s2 3p4 S 16e- [Ne] 3s2 3p4 Notation Core Electrons Longhand Configuration S 16e- 1s2 2s2 2p6 3s2 3p4 Core Electrons Valence Electrons Shorthand Configuration S 16e- [Ne] 3s2 3p4

Notation Practice Write the shorthand (noble gas) electron configuration for the following atoms: Sodium Selenium Na [Ne] 3s1 Se [Ar] 4s2 3d10 4p4

Order of Filling Orbitals

Orbitals being filled for elements in various parts of the periodic table.

CONGRATULATIONS! WOW! We sure covered a lot of territory! You have finished a very difficult, but important, chapter in Chemistry. CONGRATULATIONS!

Review your notes & do practice problems! Feeling overwhelmed? Review your notes & do practice problems!