1 Electron Configurations

– further refined Bohr’s model of the atom by developing the quantum mechanical model New Model of the Atom

3 Comparison to Bohr’s Model Bohr’s Model Quantum Mechanical Model Defines exact location of electron Gives probability of finding an electron in an area Levels are broken into sublevels Electrons in levels LevelMax # e P + and n 0 in nucleus

4 Electron configuration – the arrangement of electrons in levels and sublevels There are 4 sublevels – s p d and f. Each sublevel can be further broken down into orbitals that each hold 2 electrons. Electron Configurations

5 There are 3 rules that explain how electrons occupy levels, sublevels, and orbitals. –Aufbau principle –Pauli exclusion principle –Hund’s rule Electron Configuration Rules

6 Aufbau Principle An electron occupies the lowest-energy sublevel that can receive it.

7 How to Remember Order Period number - 2 Period number - 1Period number

8 Start at top left of periodic table. Work your way left to right. As you finish a row, move down. Remember the d sublevel’s number is one behind the period. Remember the f sublevel’s number is two behind the period. 4f follows 6s and 5f follows 7s. How to Use Periodic Table

9 Write the level and sublevel filled followed by a superscript to indicate the number of electrons in that sublevel. -s holds maximum of 2 -p holds maximum of 6 -d holds maximum of 10 -f holds maximum of 14 How to Use Periodic Table, continued

10 Electron Configurations 3d 7 Energy Level Sublevel Number of electrons in the sublevel 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 10 4p 6 5s 2 4d 10 5p 6 6s 2 4f 14 … etc.

11 OVERLAPS Why are d and f orbitals always in lower energy levels? d and f orbitals require LARGE amounts of energy to create. higher level but lower energyAccording to the Aufbau principle we must skip a sublevel that requires a large amount of energy (d and f orbtials) for one in a higher level but lower energy FOLLOW THE PERIODIC TABLE IN ORDER!

12 Let’s Try It! Write the electron configuration for the following elements: H Li N Ne K Zn Pb

13 Let’s Try It! Write the electron configuration for the following elements: H1s 1 Li 1s 2 2s 1 N1s 2 2s 2 2p 3 Ne1s 2 2s 2 2p 6 K1s 2 2s 2 2p 6 3s 2 3p 6 4s 1 Zn1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 10 Pb1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 10 4p 6 5s 2 4d 10 5p 6 6s 2 4f 14 5d 10 6p 2

14 YOU TRY THESE! Write the electron configuration for the following elements: He Mg O P S Fe Ag

15 YOU TRY THESE! Answers Write the electron configuration for the following elements: He 1s 2 Mg 1s 2 2s 2 2p 6 3s 2 O 1s 2 2s 2 2p 4 P 1s 2 2s 2 2p 6 3s 2 3p 3 S 1s 2 2s 2 2p 6 3s 2 3p 4 Fe 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 6 Ag 1s 2 2s 2 2p 6 3s 2 3p 6 4s 2 3d 10 4p 6 5s 2 4d 9

16 Noble Gas Notation A way of abbreviating long electron configurations Since we are only concerned about the outermost electrons, we can skip to places we know are completely full (noble gases), and then finish the configuration

17 Noble Gas Notation Step 1: Find the closest noble gas to the atom, WITHOUT GOING OVER the number of electrons in the atom. Write the noble gas in brackets [ ]. Step 2: Find where to resume by finding the next energy level (row in periodic table). Step 3: Resume the configuration starting with ns 2 where n is the next level

18 Noble Gas Notation Chlorine –Longhand is 1s 2 2s 2 2p 6 3s 2 3p 5 You can abbreviate the first 10 electrons with a noble gas, Neon. [Ne] replaces 1s 2 2s 2 2p 6 The next energy level after Neon is 3 So you start at level 3 on the periodic table and continue with 3s and 3p until you arrive at chlorine. [Ne] 3s 2 3p 5

19 Practice Noble Gas Notation Write the noble gas notation for each of the following atoms: Cl K Ca I Bi

20 Practice Noble Gas Notation Write the noble gas notation for each of the following atoms: Cl[Ne]3s 2 3p 5 K[Ar]4s 1 Ca[Ar]4s 2 I[Kr]5s 2 4d 10 5p 5 Bi[Xe]6s 2 4f 14 5d 10 6p 3

21 You Try These Write the noble gas notation for each of the following atoms. He Mg O P S Fe Ag

22 You Try These Write the noble gas notation for each of the following atoms. He1s 2 Mg[Ne] 3s 2 O[He] 2s 2 2p 4 P[Ne] 3s 2 3p 3 S[Ne] 3s 2 3p 4 Fe[Ar] 4s 2 3d 6 Ag[Kr] 5s 2 4d 9