Aufbau PrincipleAufbau Principle

1s2s 2p3s 3p 3d4s 4p 4d 4f5s 5p 5d 5f 5g6s 6p 6d 6f 6g 6h7s 7p 7d 7f 7g 7h 7i

e- fill lowest energy levels 1st.

nucleus

1s

2s

3s

4s

2p

3p

4p

3d

Incre

asin

g e

nerg

y

4d5s

4f5p

1

HHydrogen

1s1

2

HeHydrogen

1s2

3

LiLithium

1s22s1

4

BeBeryllium

1s22s2

5

BBoron

1s22s22p1

6

CCarbon

1s22s22p2

7

NNitrogen

1s22s22p3

8

OOxygen

1s22s22p4

9

FFluorine

1s22s22p5

10

NeNeon

1s22s22p6

11

NaSodium

[Ne]3s1

12

MgMagnesium

[Ne]3s2

13

AlAluminum

[Ne]3s23p1

14

SiSilicon

[Ne]3s23p2

15

PPhosphorus

[Ne]3s23p3

16

SSulfur

[Ne]3s23p4

17

ClChlorine

[Ne]3s23p5

18

ArArgon

[Ne]3s23p6

19

KPotassium

[Ar]4s1

20

CaCalcium

[Ar]4s2

21

ScScandium

[Ar]3d14s2

22

TiTitanium

[Ar]3d24s2

23

VVanadium

[Ar]3d34s2

24

CrChromium

[Ar]3d54s1

24

CrChromium

[Ar]3d54s1

25

MnManganese

[Ar]3d54s2

26

FeIron

[Ar]3d64s2

27

CoCobalt

[Ar]3d74s2

28

NiNickel

[Ar]3d84s2

29

CuCopper

[Ar]3d104s1

29

CuCopper

[Ar]3d104s1

30

ZnZinc

[Ar]3d104s2

31

GaGallium

[Ar]3d104s24p1

32

GeGermanium

[Ar]3d104s24p2

33

AsArsenic

[Ar]3d104s24p3

34

SeSelenium

[Ar]3d104s24p4

35

BrBromine

[Ar]3d104s24p5

36

KrKrypton

[Ar]3d104s24p6

Half-filled and filled states are preferred.

Irregular e- configurations of Cr and Cu

Chromium: A 4s electron moves to a 3d sublevel to half fill its entire 3d sublevel

Copper: A 4s electron moves to FILL its 3d sublevel

•Half filled and filled sublevels are preferred.

Orbital filling tableOrbital filling table

s1

s2

s2p1 s2p2 s2p3 s2p4 s2p5

s2p6

s2

Mendeleev’s Periodic Table (1872)Mendeleev’s Periodic Table (1872)

Dmitri Mendeleev1st to publish an organized table of elements.

Grouped elements by similar chemical properties. Arranged elements by increasing mass.

Modern Russian TableModern Russian Table

Henry Moseley (1913)Henry Moseley (1913)

Grouped elements by similar chemical properties.

Arranged elements by increasing atomic number.

Used X-Ray diffraction to determine how many protons are in an atom of an element.

The Periodic TableThe Periodic Table

PeriodGroup or Family

1

2

3

4

5

6

7

Properties of MetalloidsProperties of Metalloids

Metalloids straddle the border between metals and nonmetals on the periodic table.

Nonmetals

Metals

Metalloids

Periodic Table with Group NamesPeriodic Table with Group Names

Inner Transition Metals

Transition

Metals

Alk

ali M

eta

ls

Alk

alin

e E

art

h M

eta

ls

Halo

gen

s

Nob

le G

ases

Boro

n F

am

ily

Carb

on

Fam

ily

Nit

rog

en

Fam

ily

Oxyg

en

Fam

ily

PeriodGroup or Family

1

2

3

4

5

6

7

Trends in Atomic SizeTrends in Atomic Size

• First problem: Where do you start First problem: Where do you start measuring from?measuring from?

• The electron cloud doesn’t have a The electron cloud doesn’t have a definite edge.definite edge.

• They get around this by measuring They get around this by measuring more than 1 atom at a time.more than 1 atom at a time.

Half of the distance between nuclei in covalently bonded diatomic molecule

"covalent atomic radii"

Determination of Atomic Radius:

(e- shared)

Trends in Atomic Size Trends in Atomic Size • Influenced by three factors:Influenced by three factors:

1. Energy Level– Higher energy level is further away.Higher energy level is further away.

2. Charge on nucleus (Zeff = effective nuclear charge)

– More charge pulls electrons in closer.More charge pulls electrons in closer.3. Shielding effect– Electrons within level and from Electrons within level and from

previous levels block the effects of the previous levels block the effects of the (+) nucleus.(+) nucleus. e <-> e repulsion

Periodic TablePeriodic TableTrend forTrend for

Atomic Atomic

RadiiRadii

Size of atomdecreases

from left to right.

Size of atomincreases

from top to bottom.

Periodic Trends in Atomic Radius

Radius decreases across a period

Effective nuclear charge, Zeff, is increased. Due to: more overall charge (p+ and e-) shielding from lower levels is constant.

Group trends

• As we go down a group...

• each atom has another energy level (more shielding)

• so the atoms get bigger (Zeff is less effective).

HLi

Na

K

Rb

Periodic Trends• As you go across a period, the radius gets

smaller. (more effective nuclear charge, Zeff)

• Electrons are in same energy level.• More nuclear charge. atomic #: (p+ e-)

• Outermost electrons are closer.

Na Mg Al Si P S Cl Ar

z = 11 12 13 14 15 16 17 18

OverallOverall

Atomic Number

Ato

mic

Rad

ius

(nm

)

H

Li

Ne

Ar

10

Na

K

Kr

Rb

1st Ionization Energy - the energy required to remove the 1st electron from a mole of atoms.

375 kJ/mol Fr

He 2372 kJ/mol

376 kJ/mol Cs

403 kJ/mol Rb

419 kJ/mol K

496 kJ/mol Na

520 kJ/mol Li

1312 kJ/mol H

Ne 2081 kJ/mol

Ar 1521 kJ/mol

Kr 1351 kJ/mol

Xe 1170 kJ/mol

Rn 1037 kJ/mol

Be B C N O F

Incr

easing 1

st Ioniza

tion energ

y

Increases for successive electrons taken from the same atom

Tends to increase across a period

Electrons in the same quantum level do not shield as effectively as electrons in inner levels

    Irregularities at half filled and filled sublevels due to extra repulsion of electrons paired in orbitals, making them easier to remove

Tends to decrease down a groupOuter electrons are farther from thenucleus

Ionization Energy - the energy required to remove an electron from an atom

Table of 1Table of 1stst Ionization Energies Ionization Energies

Ionization of MagnesiumIonization of Magnesium Mg + 738 kJ Mg+ + e-

Mg+ + 1451 kJ Mg2+ + e-

Mg2+ + 7733 kJ Mg3+ + e-

1st ionization energy

2nd ionization energy

3rd ionization energy

Symbol First Second ThirdHHeLiBeBCNO F Ne

1312 2731 520 900 800 1086 1402 1314 1681 2080

5247 7297 1757 2430 2352 2857 3391 3375 3963

11810 14840 3569 4619 4577 5301 6045 6276

Symbol First Second ThirdHHeLiBeBCNO F Ne

1312 2731 520 900 800 1086 1402 1314 1681 2080

5247 7297 1757 2430 2352 2857 3391 3375 3963

11810 14840 3569 4619 4577 5301 6045 6276

ElectronegativityElectronegativity

A measure of the ability of an atom in a chemicalcompound to attract electrons

Electronegativities tend to increase across a period

Electronegativities tend to decrease down a group or remain the same

Periodic Table of ElectronegativitiesPeriodic Table of Electronegativities

Increasing electronegativ

ity

Summation of Periodic TrendsSummation of Periodic Trends

Ionic RadiiIonic Radii

Cations

Positively charged ions formed when an atom of a metal loses one or more electrons Smaller than the corresponding atom

Anions

Negatively charged ions formed when nonmetallic atoms gain one or more electrons Larger than the corresponding atom

Ion radius

Atom radius

Shielding

• The electron in the The electron in the outermost energy level outermost energy level experiences more inter-experiences more inter-electron repulsion electron repulsion (shielding).(shielding).

• Second electron has same Second electron has same shielding, if it is in the shielding, if it is in the same periodsame period

Group trends• As you go down a group, first IE As you go down a group, first IE

decreases because...decreases because...• The electron is further away.The electron is further away.• More shielding.More shielding.

Periodic trends

• All the atoms in the same period have All the atoms in the same period have the same energy level.the same energy level.

• Same shielding.Same shielding.• But, increasing nuclear chargeBut, increasing nuclear charge• So IE generally increases from left to So IE generally increases from left to

right.right.• Exceptions at full and 1/2 full orbitals.Exceptions at full and 1/2 full orbitals.

Firs

t Ion

izat

ion

ener

gy

Atomic number

He

• He has a greater IE than H.He has a greater IE than H.• same shielding same shielding • greater nuclear chargegreater nuclear charge

H

1s 2s 2pnucleus

electrons

Orbital diagram

Firs

t Ion

izat

ion

ener

gy

Atomic number

H

He Li has lower IE than H Outer electron further

away outweighs greater

nuclear charge

Li

1s 2s 2pnucleus

electrons

Orbital diagram

Firs

t Ion

izat

ion

ener

gy

Atomic number

H

He Be has higher IE than Li same shielding greater nuclear charge

Li

Be

1s 2s 2p

electrons

Orbital diagram

nucleus

Firs

t Ion

izat

ion

ener

gy

Atomic number

H

He B has lower IE than Be same shielding greater nuclear charge p orbital is slightly more

diffuse and its electron easier to remove

Li

Be

B

1s 2s 2p

electrons

nucleus

Firs

t Ion

izat

ion

ener

gy

Atomic number

H

He

Li

Be

B

C

1s 2s 2p

electrons

nucleus

Firs

t Ion

izat

ion

ener

gy

Atomic number

H

He

Li

Be

B

C

N

1s 2s 2pnucleus

Firs

t Ion

izat

ion

ener

gy

Atomic number

H

He

Li

Be

B

C

N

O

• Breaks the pattern, because the outer electron is paired in a p orbital and experiences inter-electron repulsion.

1s 2s 2pnucleus

Firs

t Ion

izat

ion

ener

gy

Atomic number

H

He

Li

Be

B

C

N

O

F

1s 2s 2pnucleus

Firs

t Ion

izat

ion

ener

gy

Atomic number

H

He

Li

Be

B

C

N

O

F

Ne• Ne has a lower IE Ne has a lower IE

than Hethan He• Both are full,Both are full,• Ne has more Ne has more

shieldingshielding• Greater distanceGreater distance

1s 2s 2pnucleus

Firs

t Ion

izat

ion

ener

gy

Atomic number

H

He

Li

Be

B

C

N

O

F

Ne Na has a lower IE than

Li Both are s1

Na has more shielding Greater distance

Na

Firs

t Ion

izat

ion

ener

gy

Atomic number

Table of 1Table of 1stst Ionization Energies Ionization Energies