Chapter 11 “Electron Configuration & Quantum Numbers”

Electron Arrangement in Atoms OBJECTIVES: Describe how to write the electron configuration for an atom.

Electron Arrangement in Atoms OBJECTIVES: Explain why the actual electron configurations for some elements differ from those predicted by the aufbau principle.

To find location & energy of e-, you must know the QUANTUM NUMBERS (click on the images below to watch an introductory video on Quantum Numbers)

QUANTUM NUMBERS After watching the videos answer the question on paper below for extra credit: a. What are the 4 quantum numbers? b. How many sublevels are there? c. What are the sublevels? d. How many electrons are there per orbital? e. What does Ms mean? f. If n = 3, what does l = ? g. How many orbitals do the following sublevels have? s, p, d, f. h. What symbol is used for the electrons spin?

QUANTUM NUMBERS Each electron in an atom has a unique set of 4 quantum numbers which describe it. 1) Principal quantum number (n) 2) Angular momentum quantum number (l) 3) Magnetic quantum number (m) 4) Spin quantum number (s)

QUANTUM NUMBERS “n” ; Principal Quantum # n = 1,2,3,4,... energy levels or periods on the periodic table max. # of e- per level = 2n2

1 2 3 4 5 6 7 Period Number Each row (or period) is the energy level. There are 7 energy levels on the PTE.

QUANTUM NUMBERS (cont) “l”; Sublevels s, p, d, f, g,... # of sublevels per energy level = n ex. n=1, l =s or n=3, l =s,p,d **the levels/sublevels fill from low to high energy Value of l 1 2 3 Type of orbital s p d f

Elements in the s - blocks Alkali metals all end in s1 Alkaline earth metals all end in s2 really should include He, but it fits better in a different spot, since He has the properties of the noble gases, and has a full outer level of electrons.

The P-block p1 p2 p3 p4 p6 p5

Transition Metals - d block d = n - 1 Note the change in configuration. s1 d5 s1 d10 d1 d2 d3 d5 d6 d7 d8 d10

The “d” orbitals fill up in levels 1 less than the period number, so the first d is 3d even though it’s in row 4. d = n - 1 1 2 3 4 5 6 7 3d 4d 5d

f1 f5 f2 f3 f4 f6 f7 f8 f9 f10 f11 f12 f14 f13 F - block Called the “inner transition elements” f = n - 2 f1 f5 f2 f3 f4 f6 f7 f8 f9 f10 f11 f12 f14 f13

1 2 3 4 5 6 7 4f 5f f orbitals start filling at 4f, and are 2 less than the period number. f = n - 2

Practice: Identify the energy level and sublevel of where the following elements are located: Al K Fe U Hg

Practice: Identify the energy level, sublevel and column of where the following elements are located: Al: 3p1 K: 4s1 Fe: 3d6 U: 5f4 Hg: 5d1

Aufbau Principle: - e- enter levels/sublevels of lowest energy 1st (1s, 2s, 2p, 3s, 3p, 4s, )

Practice: Now identify the energy level and sublevel configuration of the following elements: Al K Fe U Hg

Practice: Now identify the energy level and sublevel configuration of the following elements: Al: 1s,2s,2p,3s,3p K: 1s,2s,2p,3s,3p,4s Fe: 1s,2s,2p,3s,3p,4s,3d Hg: 1s,2s,2p,3s,3p,4s,3d,4p,5s,4d,5p,6s,4f,5d

QUANTUM NUMBERS (cont) “m”; Orbitals determines the # of e- held in the sublevels & their position n2 = total orbitals per energy level ex. n=1, 1 orbital, n=3, 9 orbitals Orbitals are filled in order of increasing energy, with no more than two electrons per orbital

QUANTUM NUMBERS (cont) “m”; Orbitals (cont) s = 1 orbital & 1 pr. of e- p = 3 orbitals & 3 pr. of e- d = 5 orbitals & 5 pr. of e- f = 7 orbitals & 7 pr. of e- *only 1 pr. of e- per orbital

2 6 10 14 Summary Starts at energy level s 1 1 p 3 2 d 5 3 7 4 f Maximum electrons Starts at energy level # of (orbitals) 2 s 1 1 p 3 6 2 10 d 5 3 7 14 4 f

Quantum Number, ml Describes the three-dimensional orientation of the orbital. Values are integers ranging from -l to l: −l ≤ ml ≤ l. Therefore, on any given energy level, there can be up to 1 s orbital, 3 p orbitals, 5 d orbitals, 7 f orbitals, etc.

Quantum Number, ml Orbitals with the same value of n form a shell. Different orbital types within a shell are subshells.

QUANTUM NUMBERS (cont) “s”; Spin rotation of e- each pair of e- must have opposite spins: +1/2 or -1/2 or _ _

To find location & energy of e-, you must know the QUANTUM NUMBERS (click on the image below to watch a review video on Quantum Numbers – watch to the 4:20 mark)

Electron Configurations The way in which electrons are distributed among the various orbitals is called the electron configuration. Watch the video for how to write the electron configurations of elements

Writing Electron Configuration Mg=12 1. e- enter energy levels of lowest energy 1st (1s2, 2s2, 2p6, 3s2) Try it with these elements: Al: 1s22s22p63s23p1 K: 1s22s22p63s23p64s1 Fe; 1s22s22p63s23p64s23d6 Hg: 1s2,2s2,2p6,3s2,3p6,4s2,3d10,4p6,5s2,4d10,5p6,6s2,4f14,5d10

H 1 Li 3 Na 11 K 19 Rb 37 Cs 55 Fr 87 1s1 1s22s1 1s22s22p63s1 1s22s22p63s23p64s1 1s22s22p63s23p64s23d104p65s1 1s22s22p63s23p64s23d104p65s24d10 5p66s1 1s22s22p63s23p64s23d104p65s24d105p66s24f14 5d106p67s1 Do you notice any similarity in these configurations of the alkali metals?

Do you notice any similarity in the configurations of the noble gases? 1s22s22p6 1s22s22p63s23p6 1s22s22p63s23p64s23d104p6 1s22s22p63s23p64s23d104p65s24d105p6 1s22s22p63s23p64s23d104p65s24d10 5p66s24f145d106p6 He Do you notice any similarity in the configurations of the noble gases? 2 Ne 10 Ar 18 Kr 36 Xe 54 Rn 86

Look at the electron configurations for these elements: Titanium - 22 electrons 1s22s22p63s23p64s23d2 Vanadium - 23 electrons 1s22s22p63s23p64s23d3 Chromium - 24 electrons 1s22s22p63s23p64s23d4 (expected) But this is not what happens!!

Chromium is actually: 1s22s22p63s23p64s13d5 Why? This gives us two half filled orbitals (the others are all still full) Half full is slightly lower in energy. The same principal applies to copper.

Copper’s electron configuration Copper has 29 electrons so we expect: 1s22s22p63s23p64s23d9 But the actual configuration is: 1s22s22p63s23p64s13d10 This change gives one more filled orbital and one that is half filled. Remember these exceptions: d4, d9

Irregular configurations of Cr and Cu Chromium steals a 4s electron to make its 3d sublevel HALF FULL Copper steals a 4s electron to FILL its 3d sublevel

Writing Orbital Notation Watch the video on writing Orbital Notation before going on.

Writing Orbital Notation Try it with these elements: Al K Fe Hg

Writing Orbital Notation Use your PTE Determine the number of e-’s Determine the energy levels Write the electron configuration Determine the orbitals needed Write the orbital notation using arrows

Hund’s Rule: When occupying orbitals of equal energy, 1 e- enters each orbital (with same spin) until all orbitals have 1 e- Only after all orbitals in a sublevel are half- filled do electrons “pair up.”

Writing Orbital Notation Al: 1s22s22p63s23p1 __, __, __ __ __, __, __ __ __ K: 1s22s22p63s23p64s1 __, __, __ __ __, __, __ __ __, __ Fe; 1s22s22p63s23p64s23d6 __, __, __ __ __, __, __ __ __, __, __ __ __ __ __ Hg: 1s2,2s2,2p6,3s2,3p6,4s2,3d10,4p6,5s2,4d10,5p6,6s2,4f14,5d10 __, __ __ __ __ __ __ __, __ __ __ __ __

Pauli Exclusion Principle No two electrons in an atom can have the same four quantum numbers. To show the different direction of spin, a pair in the same orbital is written as: Wolfgang Pauli

Writing Electron-Dot Diagrams Mg = 12 Electron Configuration Orbital Notation Use only valence electrons and orient to the orbital notation Watch how-to video:

Writing Electron-Dot Diagrams Try it with these elements: Al K Fe U Hg