week 7/th: lecture units ‘17 & 18’ - chemistry€¦ · now we are ready to fill up the...

Week 7/Th: Lecture Units ‘17 & 18’

© DJMorrissey, 2o12

Unit 16: Electron standing waves -- uncertainty, quantum numbers -- properties of standing waves -- shapes and nodes, labels -- electron-electron repulsion Unit 17: Electron orbitals -- electron spin -- electron configurations Unit 18: Periodicity -- periodicity of elements -- radii, ionization, affinity -- electronegativity Unit 19: Chemical Bonding Issues: ? Homework #5 due this Saturday, Oct. 13th 8am

With many electrons, the energy depends on “n” and also slightly on “l”

Week 7/Th: Many-Electron Energy Levels


1s

2s

3d

4f En

ergy

(J)

2p 3s

3p 4s 4p

4d

He 2 Ne 10 Ar 18 Kr 36 Xe 54 Rn 86

It would be good if we found a factor of two …

1

4 4

Week 7/Th: Electron Magnetism – Spin


Continued studies of the electron [and the proton and neutron] showed that they each have a magnetic moment – that is, each particle behaves as if it is a tiny magnet. Similar to a compass needle in the earth’s magnetic field, an electron can have two stable positions in a magnetic field: exactly aligned with the field or exactly anti-aligned, nothing in-between will be stable. This is feature is called “spin” because a rotating electric charge creates a magnetic field.

Here we find our missing factor of two. We can put two electrons into each orbital if we pair the magnetic moments. A fourth quantum number that, combined with the other three, is used to identify each electron in an atom.

Spin “up” é Spin “down”, ê

Week 7/Th: Energy Levels for Shoes

© DJMorrissey, 2oo9

Linda Bennett – Boise State Univ. Edtech2.boisestate.edu/lindabennett1/502/Periodic Table e config/electron configuration.html

Now we are ready to fill up the energy level diagram with electrons. 1)  Fill from the bottom (duh). Lowest energy, “Aufbau” 2)  Only two electrons with opposite spins per orbital. “Exclusion” 3)  Electrons spread out, align spins among degenerate orbitals.

“Maximum Multiplicity” .. “Maximum Spin” QN Labels: (n, l, ml) mS

Week 7/Th: Fill up Energy Levels -1a-


1s

Ener

gy (J

)

2p

3s

l =0 1

Hydrogen, 1e- (1,0,0) +1/2 or (1,0,0) -1/2 [only one electron so no difference for spin] or 1s1

é

2s

Helium, 2e- (1,0,0) +1/2 for one (1,0,0) -1/2 for the other. or 1s2

ê


“Maximum Multiplicity” .. “Maximum Spin” QN Labels: (n, l, ml) mS

Week 7/Th: Fill up Energy Levels -1b-


1s

2s

Ener

gy (J

)

2p

3s

l =0 1

Lithium, 3e- (1,0,0) +1/2 for one (1,0,0) -1/2 for the next Then a choice (2,0,0) +1/2 or (1,0,0) -1/2 or 1s22s1

é

é

ê

Beryllium, 4e- (1,0,0) +1/2 for one (1,0,0) -1/2 for the next (2,0,0) +1/2 for the next (2,0,0) -1/2 for the last or 1s22s2

ê


“Maximum Multiplicity” .. “Maximum Spin”

Week 7/Th: Fill up Energy Levels -2-


1s

2s

Ener

gy (J

)

2p

3s

l =0 1

Boron, 5e- (1,0,0) +1/2 for one (1,0,0) -1/2 for the next (2,0,0) +1/2 for the next (2,0,0) -1/2 for the next SIX choices for next one !!! or 1s22s22p1 (2,1,-1) +1/2 (2,1,0) +1/2 (2,1,1) +1/2 (2,1,-1) -1/2 (2,1,0) -1/2 (2,1,1) -1/2

é

é

é

ê

ê é

é

é

ê

ê é

é

ê

ê

ê

?

How about Manganese Z=25 ?

Week 7/Th: Many-Electron Energy Levels -1-


1s

2s

3d

4f En

ergy

(J)

2p 3s

3p 4s 4p

4d

Mn

Manganese, 25e- 1s22s22p63s23p6 4s23d5 [Ar] 4s23d5

é é é é é

é é é é é

How about Ruthenium Z=44 ?

Week 7/Th: Many-Electron Energy Levels -2-


1s

2s

3d

4f En

ergy

(J)

2p 3s

3p 4s 4p

4d

Ru

Ruthenium, 44e- 1s22s22p63s23p6 4s23d104p6 5s24d6 [Kr] 5s24d6

é é êé é é

éê é é é é

Week 7/Th: Predict Elemental Properties!


The simple filling of the atomic energy levels provides a basis for understanding a wide range of chemical behavior. •  Atomic Radii and Iso-electronic Radii •  Ionization Potential •  Electron Affinity •  Electronegativity

Week 7/Th: Atomic Radii


Cl1.02

S1.05

Ne0.58

F0.57

N0.71

O0.66

Be0.96

Sc1.70

Al1.21

C0.76

B0.84

He0.28

Li1.28

H0.31

Mg1.41

Na1.66

Ca1.76

K2.03

Sr1.95

Rb2.20

Y1.90

Ti1.60

Zr1.75

V1.53

Nb1.64

Cr1.39

Mo1.54

Mn1.39

Tc1.47

Fe1.32

Ru1.46

Co1.26

Rh1.42

Ni1.24

Pd1.39

Cu1.32

Ag1.45

Zn1.22

Cd1.44

Ga1.22

In1.42

Tl1.45

Ba2.15

Cs2.44

Lu1.87

Hf1.75

Ta1.70

W1.62

Re1.51

Os1.44

Ir1.41

Pt1.36

Au1.36

Hg1.32

Ge1.20

Sn1.39

Pb1.46

Sb1.39

Bi1.48

Si1.11

As1.19

Te1.38

Ar1.06

Kr1.16

Xe1.40

Rn1.50

P1.07

Se1.20

Br1.20

I1.39

Periodic Table of the ElementsCollege of Saint Benedict / Saint John's University

Po 1.48

At1.50

Ra2.21

Fr2.60

Ce2.04

La2.07

Pr2.03

Nd2.01

Pm1.99

Sm1.98

Eu1.98

Gd1.96

Tb1.94

Dy1.92

Ho1.92

Er1.89

Tm1.90

Th2.06

Ac2.15

Pa2.00

U1.96

Np1.90

Pu1.87

Am1.80

Cm1.69

Yb1.87

With covalent radii in Αngstroms (10-10 m); based on data from Cambridge Crystallographic Database.1

1. Beatriz Cordero et al. Dalton Trans. 2008, 21,:2832–2838.

Neutral atoms: covalent radii extracted from data from simple molecules. Unfortunately, two variables the number of electrons and number of protons.

Week 7/Th: Iso-electronic Radii


2 e- n=1 10 e- n=2 18 e- n=3 36 e- n=4 54 e- n=5

Iso-electronic atoms and ions have the same number of electrons but the charge on the nucleus is different. Only one variable (atomic number). Larger charge on nucleus, same Principal QN .. Smaller radius.

Week 7/Th: Ionization Energy


The ionization energy is the minimum amount of energy to remove the least-bound electron from a neutral atom. E.g., He (g) à He+ + e- + ΔE

1s

2s

Ener

gy (J

) 2p

3s 3p

4s 4p 3d

S & P block elements have a pattern of 2,3,3

Week 7/Th: Ionization Energy


The ionization energy is the minimum amount of energy to remove the least-bound electron from a neutral atom. E.g., He (g) à He+ + e- + ΔE

Week 7/Th: Electron Affinity


The electron affinity is the energy change when an electron is added to a neutral atom. E.g., 6C (g) + e- à 6C- (g) + ΔE compared to 7N (g) + e- à 7N- (g) + ΔE’

1s

2s

Ener

gy (J

) 2p

3s 3p

4s 4p 3d

ê

é

é

ê

ê

ê

ê é

Week 7/Th: Electronegativity


The electronegativity is a function that combines the ionization potential and the electron affinity to describe the relative ability of an atom to “attract” electrons to itself that was introduced by Linus Pauling and elaborated by others. Remember both of these functions follow the same pattern in the Periodic Table.

We will use electronegativity next week to describe electron sharing in bonds.

week 7/th: lecture units ‘17 & 18’ - chemistry€¦ · now we are ready to fill up the...

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