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What’s coming up???• Oct 25 The atmosphere, part 1 Ch. 8• Oct 27 Midterm … No lecture• Oct 29 The atmosphere, part 2 Ch. 8• Nov 1 Light, blackbodies, Bohr Ch. 9• Nov 3,5 Postulates of QM, p-in-a-box Ch. 9• Nov 8,10Hydrogen and multi – e atoms Ch. 9• Nov 12, 15 Multi-electron atoms Ch.9,10• Nov 17 Periodic properties Ch. 10• Nov 19 Periodic properties Ch. 10• Nov 22 Valence-bond; Lewis structures Ch. 11• Nov 24 Hybrid orbitals; VSEPR Ch. 11, 12• Nov 26 VSEPR Ch. 12• Nov 29 MO theory Ch. 12• Dec 1 MO theory Ch. 12• Dec 2 Review for exam

Hydrogen has its one electron in the 1s orbital:1s 2s 2p

H:

1s 2s 2pHe:

1s 2s 2pHe:

helium ground state

Helium has two electrons:

1s1

1s12s1

1s2

ORBITAL DIAGRAM

Now onto the next atoms

Helium can also exist in an excited state such as:

with opposite spins: both occupy the 1s orbital

Pauli principle

Lithium has three electrons, so it must use the 2s orbital:

Beryllium has four electrons, which fill both the 1s and 2s orbitals:

Boron’s five electrons fill the 1s and 2s orbitals, and begin to fill the 2p orbitals. Since all three are degenerate, the order in which they are filled does not matter.

1s 2s 2pLi: 1s22s1

1s 2s 2pBe: 1s2 2s2

1s 2s 2pB: 1s22s22p1

1s 2s 2pC: 1s22s22p2

1s 2s 2pC: 1s22s22p2

How can we decide?????

A CHOICE

OR

CARBON Z=6

HUND’S RULEFOR THE GROUND STATE

ELECTRONS OCCUPY DEGENERATE ORBITALS SEPARATELY

THE SPINS ARE PARALLEL

SO FOR CARBON THE GROUND STATE IS

1s 2s 2pC: 1s22s22p2

1s 2s 2pNe: 1s22s22p6

1s 2s 2pF: 1s22s22p5

1s 2s 2pO: 1s22s22p4

1s 2s 2pN: 1s22s22p3

Nitrogen

Oxygen

Fluorine

Neon

THE ELECTRON CONFIGURATIONS FOR NITROGEN TO NEON

The valence electron configuration of the elements in the periodic table repeat periodically!

H He1s1 1s2

Li Be B C N O F Ne2s1 2s2 2p1 2p2 2p3 2p4 2p5 2p6

Na Mg Al Si P S Cl Ar3s1 3s2 3p1 3p2 3p3 3p4 3p5 3p6

Every element in a group has

the same valence electron configuration!

Sodium has the electron configurationNa: 1s22s22p63s1

abbreviate electron configurations by ...

1s22s22p63s23p64s23d104p65s1And Rb is:

dividing the electrons into……..

valence electrons and core electrons.

What does this mean?????

Example Na: 1s22s22p63s1

VALENCE ELECTRONS

Noble gases have fully-filled valence shells

Example Ar: 1s22s22p63s23p6

are the electrons in the outermost principle quantum level of an atom.

highest value of n.

Valence electrons are the ones involved in bonding.

CORE ELECTRONS

can be abbreviated as a noble gas core and the valence electrons.

The configuration for sodium is:

Na: 1s22s22p63s1

or Na: [Ne]3s1

ELECTRON CONFIGURATIONS

Now we can easily write the electron configurations…..

QUESTION…..

1s

E

2s2p

3s3p

3d4s4p

5s4d

POTASSIUM ELECTRONIC CONFIGURATION

1s22s22p62p23s23p64s1 or [Ar]4s1

Q: why does 3d lie above 4s??

SCREENING AND PENETRATION

PENETRATION Is to get close to the nucleus

SCREENING Is to block the view of other electrons of the nucleus

Consider the excited state of helium

1s13p1

LOOK AT RADIAL PROBABILITY DISTRIBUTIONS

0

0.1

0.2

0.3

0.4

0.5

0.6

0 5 10 15 20 25 30

SCREENING AND PENETRATION

THE 1s close to the nucleusPENETRATES WELL SEES A CHARGE OF Z=2

EFFECTIVE NUCLEAR CHARGE…...

Is

3p

THE 3p DOES NOT SCREEN THE NUCLEUS

0

0.1

0.2

0.3

0.4

0.5

0.6

0 5 10 15 20 25 30

SCREENING AND PENETRATION

THE 1s close to the nucleusEFFECTIVE NUCLEAR CHARGE Zeff = 2

ENERGY MORE NEGATIVE THAN IN H-ATOM

Is

3p

E 2.178 x 10-19n

Zneff 2

0

0.1

0.2

0.3

0.4

0.5

0.6

0 5 10 15 20 25 30

SCREENING AND PENETRATION

THE 3p far from the nucleus

PENETRATES POORLY 1s SCREENS 3p WELL

SEES A CHARGE OF Zeff = Z – S = 2-1 = 1

Is

3p

0

0.02

0.04

0.06

0.08

0.1

0.12

0 5 10 15 20 25 30

THE 3s orbital penetrates better than 3p orbital

3s3p3d

The 3p orbital penetrates better than 3d orbital

Zeff(s) > Zeff(p) > Zeff(d)

0

0.05

0.1

0.15

0.2

0.25

0 5 10 15 20 25 30

So, in a multi-electron atom Zeff(s) > Zeff(p) > Zeff(d)

E4s < E3d

ENERGY LEVELS REVERSE!!E A

Znneff 2

2

The first transition element is scandium, Sc (Z=21)

H He1s1 1s2

Li Be B C N O F Ne2s1 2s2 2p1 2p2 2p3 2p4 2p5 2p6

Na Mg Al Si P S Cl Ar3s1 3s2 3p1 3p2 3p3 3p4 3p5 3p6

K Ca

Scandium has the electron configuration:Sc: [Ar]4s23d1

Sc

TRANSITION METALS.

Because…..

1s

E

2s2p

3s3p

3d4s4p

5s4d

ENERGY LEVEL DIAGRAM FOR A MULTI-ELECTRON ATOM

SCANDIUM ELECTRONIC CONFIGURATION

Scandium is the first TRANSITION ELEMENT

Sc: [Ar]4s23d1

the metals that fill the d orbitals in their valence shell.

TRANSITION METALS

HUND’S RULE OBEYED FOR ALL EXCEPT

Cr and Cu

Cr: [Ar] 4s23d4EXPECTED

OBSERVED Cr: [Ar] 4s13d5 …. The d-shell is ½ filled this way; all spin up

WHEN n=3

FOR COPPER

the metals that fill the d orbitals in their valence shell.

TRANSITION METALS

HUND’S RULE OBEYED FOR ALL EXCEPT

Cr and Cu

Cu: [Ar] 4s23d9EXPECTED

OBSERVED Cu: [Ar] 4s13d10 …. The d-shell is filled this way – extra stable

WHEN n=3

IONS…...