Orbital Notation, Valence Electrons & Lewis Dot Structures

Electron Configuration Rules Aufbau Principle Each electron MUST occupy the lowest energy orbital available first Pauli Exclusion Principle A maximum of 2 electrons can occupy a single orbital, but only if the electrons have opposite spins 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

Aufbau Principle Each electron MUST occupy the lowest energy level and sublevel available first 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

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

Pauli Exclusion Principle A maximum of 2 electrons can occupy a single orbital, but only if the electrons have opposite spins 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: 1st energy level = 1 sublevel and 1 orbital = max 2 electrons 2nd & 7th energy level = 2 sublevels and 4 orbitals = max 8 electrons 3rd & 6th energy level = 3 sublevels and 9 orbitals = max 18 electrons 4th – 5th energy levels = 4 sublevels and 16 orbitals = max 32 electrons Remember that d and f sublevels are behind s and p

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 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 – 1s22s1 _________ _________ 1s 2s

Hund’s Rule Orbital Notation Let’s Try Nitrogen: 1s22s22p3 ___________ _____________ __________ ___________ ___________ 1s 2s 2p *This is called an orbital diagram/notation

A little more of a challenge: Sulfur 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

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

Valence Electrons 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: 1s2 2s2 2p6 3s2 3p5 The outermost energy level is the 3rd energy level Chlorine has 7 valence electrons (2 + 5 = 7)

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

Valence Electrons THERE IS AN EASIER WAY!!!!

Lewis Dot Structure A model that uses electron-dot structures to show how electrons are arranged in molecules. 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 Al

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

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