E LECTRON C ONFIGURATION

H OW M ANY E LECTRONS ARE I N AN A TOM ? In an ATOM, # Electrons = # Protons = Atomic Number Li 3 6, lithium

3 W AYS TO T ELL H OW M ANY E LECTRONS TypeProsCons Atomic Number Quick and easy, just look at PToE Doesn’t tell us about arrangement of electrons

3 W AYS TO T ELL H OW M ANY E LECTRONS TypeProsCons Atomic Number Quick and easy, just look at PToE Doesn’t tell us about arrangement of electrons Electron Configuration Shows where the electrons are Doesn’t tell us which ones can bond

3 W AYS TO T ELL H OW M ANY E LECTRONS TypeProsCons Atomic Number Quick and easy, just look at PToE Doesn’t tell us about arrangement of electrons Electron Configuration Shows where the electrons are Doesn’t tell us which ones can bond Lewis (Electron) Dot Diagram Shows us how many electrons can bond Doesn’t tell us total electrons

3 W AYS TO T ELL H OW M ANY E LECTRONS TypeProsCons Atomic Number Quick and easy, just look at PToE Doesn’t tell us about arrangement of electrons Electron Configuration Shows where the electrons are Doesn’t tell us which ones can bond Lewis (Electron) Dot Diagram Shows us how many electrons can bond Doesn’t tell us total electrons Yesterday Today Tomorrow

B ACKGROUND I NFORMATION Energy Level – distance away from the nucleus in which electron “resides” -Think Bohr model- Represented by 1, 2, 3, 4…

B ACKGROUND I NFORMATION Orbital – regions in energy levels that have similar shapes Represented by s, p, d, f

B ACKGROUND I NFORMATION s = Sphere

B ACKGROUND I NFORMATION p = dumbbell

B ACKGROUND I NFORMATION d = clover

f= complicated Care to try?? B ACKGROUND I NFORMATION

S TEPS FOR DETERMINING E LECTRON C ONFIGURATION 1. Find the atomic number of the element – this is # electrons Atomic # = 3 Li has 3 electrons StepExample - Li

S TEPS FOR DETERMINING E LECTRON C ONFIGURATION 2. Put the electrons in their orbitals 3 electrons StepExample - Li

S TEP 2 Pauli Exclusion Principle – no more than two electrons per orbital

S TEP 2 Aufbau Principle – electrons fill lowest energies first

S TEP 2 Hund’s Rule - Electrons will stay unpaired in each energy level for as long as possible

S TEPS FOR DETERMINING E LECTRON C ONFIGURATION 3. Write electron configuration 3 electrons StepExample - Li

S TEPS FOR DETERMINING E LECTRON C ONFIGURATION Report: Energy Level Orbital # electrons

S TEPS FOR DETERMINING E LECTRON C ONFIGURATION 3. Write electron configuration. 3 electrons StepExample - Li 1s22s11s22s1

E XAMPLE 2 - Sulfur Atomic # = 16 Electron Configuration: 1s 2 2s 2 2p 6 3s 2 3p 4

E XAMPLE 3 - Arsenic Atomic # = 33 Electron Configuration: 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 10 4p 3

E XAMPLE 4 - Carbon Atomic # = 6 Electron Configuration: 1s 2 2s 2 2p 2

G ETTING INTO AN E XCITED S TATE An electron in an excited state is in a higher state (orbital and/or energy level) than it usually is Ground state – normal level for an electron

E XCITED S TATE When the electron receives energy it jumps from the ground state to a higher level This electron will then fall back down to the ground state

E XCITED S TATE - W HAT ’ S IT LOOK LIKE ? Remember the Lithium ground state? 1s 2 2s 1 What if we make an electron excited? It’ll jump up in energy! sp Excited State Lithium- 1s 2 2p 1

O N Y OUR O WN Try Helium, Oxygen, Calcium, and Bromine with a Partner Then do the rest BY YOURSELF!! (Ask QUESTIONS when you need!!)