Orbital Notation, Valence Electrons & Lewis Dot Structures 1.Get out your notes 2.Wait quietly

1.Aufbau Principle  Each electron MUST occupy the lowest energy orbital available first 2.Pauli Exclusion Principle  A maximum of 2 electrons can occupy a single orbital, but only if the electrons have opposite spins 3.Hund’s Rule  Single electrons with the same spin must occupy each equal energy orbital before additional electrons with opposite spins can occupy those same orbitals Electron Configuration Rules

 Determine the order of energy levels, sub-levels, and the orbitals within the sub-levels  Energy levels are in the order of the periods down the periodic table  Order: 1, 2, 3, 4, 5, 6, and 7  Sub-levels: are in the order of s, p, d, and f Aufbau Principle Each electron MUST occupy the lowest energy level and sublevel available first

 Notice that d and f sub-levels are “behind” s and p sub-levels Aufbau Principle:

 Remember the amount of orbitals in each sub-level  S-sublevel = 1 orbital = 2 electrons  P-sublevel = 3 orbitals = 6 electrons  D-sublevel = 5 orbitals = 10 electrons  F=sublevel = 7 orbitals = 14 electrons  Each energy level holds a set amount of electrons:  1 st energy level = 1 sublevel and 1 orbital = max 2 electrons  2 nd & 7 th energy level = 2 sublevels and 4 orbitals = max 8 electrons  3 rd & 6 th energy level = 3 sublevels and 9 orbitals = max 18 electrons  4 th – 5 th energy levels = 4 sublevels and 16 orbitals = max 32 electrons  Remember that d and f sublevels are behind s and p Pauli Exclusion Principle A maximum of 2 electrons can occupy a single orbital, but only if the electrons have opposite spins

 Orbital Notation:  Shows the electrons in an orbital and their spin  S- 1 orbital, p- 3 orbitals, d – 5orbitals, and f – 7 orbitals  Lines/boxes represent the orbitals  The number of the energy level and its sublevel are written below the line  Uses up and down arrows to represent the electrons and their spins  Example: Lithium – 1s 2 2s 1_________ 1s 2s Hund’s Rule Single electrons with the same spin must occupy each equal energy orbital before additional electrons with opposite spins can occupy those same orbitals

 Let’s Try Nitrogen:  1s 2 2s 2 2p 3 __________________________________ ___________ ___________ 1s 2s 2p *This is called an orbital diagram/notation Hund’s Rule Orbital Notation

 What is Sulfur’s electron configuration? ________________________________________________________  What is Sulfur’s orbital notation? *Remember: S- 1 orbital, p- 3 orbitals, d – 5orbitals, and f – 7 orbitals A little more of a challenge: Sulfur

 Write the orbital diagrams for the following elements: Manganese Potassium Gallium Your Turn: Complete these in your notes

 The electrons that determine the chemical properties of an element  The electrons in the highest (outermost) energy level  How do we know what is the highest/outermost energy level?  The electron configuration for Chlorine is: 1s 2 2s 2 2p 6 3s 2 3p 5 The outermost energy level is the 3 rd energy level Chlorine has 7 valence electrons (2 + 5 = 7) Valence Electrons

 How many valence electrons are found in the following atoms? Valence Electrons ElementElectron Configuration# of Valence Electrons Sodium Carbon Gallium Oxygen Fluorine

Valence Electrons THERE IS AN EASIER WAY!!!!

 Shows the valence electrons around the element symbol  What is an element symbol?  Aluminum =  Aluminum has _____ valence electrons  Imagine aluminum symbol with a box around it *Each side of the box can only hold 2 electrons *Put 1 dot (to represent 1 electron) on each side before adding a second dot to that side of the box – Pauli’s Exclusion Principle So the final product looks like this: Al Lewis Dot Structure A model that uses electron-dot structures to show how electrons are arranged in molecules. Al

How many valence electrons does Sulfur have? ______ S Give Sulfur a try:

 Draw the Lewis Dot Structure for the following elements: Your turn: Complete these in your notes ElementSymbol and number of valence electrons Lewis Dot Structure Lithium Nitrogen Calcium Bromine Carbon Selenium

Work on your homework: Page 7 in packet and prelab REMEMBER: LAB TOMORROW YOU MUST BE DRESSED IN LAB ATTIRE  Closed shoes  Long pants (no skin, not even ankles)  NO baggie sleeves  Hair pulled back Until the Bell Rings: