8.11 electron configurations

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8.11 Electron Configurations 8.11 Electron Configurations Noble Gas Electron Configuration 1s 2s 2p Ne (Z=10) Valence electrons (orbitals with highest n) Inner shell e - Noble gases are unusually stable because they have completely filled orbitals Filled octet: 8e - They don’t want to gain or lose e - 8.11 Electron Configurations 8.11 Electron Configurations Noble Gas Electron Configuration 1s 2s 2p Ne (Z=10) To simplify the notation, chemists use the following notation to represent filled inner shells: [Noble Gas Chemical Symbol] [Ne] stands for 1s 2 2s 2 2p 6 8.12 e 8.12 e - Configurations & The Periodic Table Configurations & The Periodic Table 8.12 e - Configurations & Periodic Table 8.12 e 8.12 e - Configurations & The Periodic Table Configurations & The Periodic Table Important Point The filling order table provides a general guide…there are exceptions…we will discuss them 8.12 e 8.12 e - Configurations & The Periodic Table Configurations & The Periodic Table Groups run down…Periods run across Table Group 1 8.12 e 8.12 e - Configurations & The Periodic Table Configurations & The Periodic Table Groups run down…Periods run across Table Period 4 Group 1

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8.11 Electron Configurations8.11 Electron Configurations

Noble Gas Electron Configuration

1s 2s 2p

Ne (Z=10)

Valence electrons (orbitals with highest n)

Innershelle-

Noble gases are unusually stable becausethey have completely filled orbitals

Filled octet: 8e-

They don’t want to gain or lose e-

8.11 Electron Configurations8.11 Electron ConfigurationsNoble Gas Electron Configuration

1s 2s 2p

Ne (Z=10)

To simplify the notation, chemists use thefollowing notation to represent filled innershells:

[Noble Gas Chemical Symbol]

[Ne] stands for 1s22s22p6

8.12 e8.12 e-- Configurations & The Periodic TableConfigurations & The Periodic Table

8.12 e- Configurations & Periodic Table

8.12 e8.12 e-- Configurations & The Periodic TableConfigurations & The Periodic Table

Important Point The filling order table

provides a general guide…there are

exceptions…we will discuss them

8.12 e8.12 e-- Configurations & The Periodic TableConfigurations & The Periodic Table

Groups run down…Periods run across Table

Group 1

8.12 e8.12 e-- Configurations & The Periodic TableConfigurations & The Periodic Table

Groups run down…Periods run across Table

Period 4

Group 1

8.12 e8.12 e-- Configurations & The Periodic TableConfigurations & The Periodic Table

Elements in same group have same electron

configurations

8.12 e8.12 e-- Configurations & The Periodic TableConfigurations & The Periodic Table

Group 1ns1

Group 17ns2np5

Group 18Noble gases

ns2np6

Excepthelium

1 valence e-

7 valence e-

“Octet”

8.12 e8.12 e-- Configurations & The Periodic TableConfigurations & The Periodic Table

Group 1ns1

Group 17ns2np5

Group 18Noble gases

ns2np6

Excepthelium

1 valence e-

7 valence e-

“Octet”

Note: Quantum Number n corresponds to the Period Number

8.12 e8.12 e-- Configurations & The Periodic TableConfigurations & The Periodic Table

Group 1ns1

Group 18ns2np6

Group 17ns2np5 *

* Except He

8.12 e8.12 e-- Configurations & The Periodic TableConfigurations & The Periodic Table

Refer to “blocks” in the periodic table

according to which orbitals are being filled

s block, p block, d block, f block

s block & p block are Main Group Elements

d block are Transition Metals

f block are Lanthanides & Actinides (Rare- earth elements)

8.12 e8.12 e-- Configurations & The Periodic TableConfigurations & The Periodic Table

s blockMain Group Elements

p block

Filling nsorbitals

Filling nporbitals

8.12 e8.12 e-- Configurations & The Periodic TableConfigurations & The Periodic Table

s block

d blockTransition metals

p block

Filling (n-1)dorbitals

8.12 e8.12 e-- Configurations & The Periodic TableConfigurations & The Periodic Table

s block

d blockTransition metals

f block

p block

Filling (n-2)f orbitals

8.12 e8.12 e-- Configurations & The Periodic TableConfigurations & The Periodic Table

f orbitals start filling after lanthanum (Z=57) &

after actinium (Z=89)

La [Xe]5d16s2

Ac [Rn]6d17s2

Then the f orbitals start filling…# = no. of e-

[Xe]4f#5d16s2

[Rn]5f#6d17s2

Note La & Ac are d block f block

When f orbitals are filled…filling of the d resumes

8.12 e8.12 e-- Configurations & The Periodic TableConfigurations & The Periodic Table

Note there are exceptions to the filling table

La [Xe]5d16s2

Ac [Rn]6d17s2

[Xe]4f#5d16s2

[Rn]5f#6d17s2

f block

One electrongoes into the6d orbitalbefore fillingthe 5f

One electrongoes into the5d orbitalbefore fillingthe 4f

You are not responsiblefor knowing this

8.12 e8.12 e-- Configurations & The Periodic TableConfigurations & The Periodic Table

f orbitals start filling after lanthanum (Z=57) &

after actinium (Z=89)

La [Xe]5d16s2

Ac [Rn]6d17s2

Many filling exceptions in the f block…you are not responsible for knowing theexceptions within the f block

Then the f orbitals start filling…# = no. of e-

[Xe]4f#5d16s2

[Rn]5f#6d17s2

f block

When f orbitals are filled…filling of the d resumes

8.12 e8.12 e-- Configurations & The Periodic TableConfigurations & The Periodic Table

s block

d blockTransition metals

f block

p block

8.12 e8.12 e-- Configurations & The Periodic TableConfigurations & The Periodic Table

s block ns#, n comes from period

8.12 e8.12 e-- Configurations & The Periodic TableConfigurations & The Periodic Table

s block ns#, n comes from period1s 1s

2s

4s3s

6s5s

7s

8.12 e8.12 e-- Configurations & The Periodic TableConfigurations & The Periodic Table

p blockp block ns2np# n comes from period

8.12 e8.12 e-- Configurations & The Periodic TableConfigurations & The Periodic Table

p blockp block ns2np#, n comes from period

2p

4p3p

6p5p

8.12 e8.12 e-- Configurations & The Periodic TableConfigurations & The Periodic Table

d blockTransition metals

d block ns2(n-1)d#, n comes from period

8.12 e8.12 e-- Configurations & The Periodic TableConfigurations & The Periodic Table

d blockTransition metals

d block ns2(n-1)d#, n comes from period

4d3d

6d5d

8.12 e8.12 e-- Configurations & The Periodic TableConfigurations & The Periodic Table

d blockTransition metals

d block ns2(n-1)d#, n comes from period

4d3d

6d5d

Note exceptions like Cr & Cu due to half-filled and filled d orbitalsYou are responsible for knowing these

8.12 e8.12 e-- Configurations & The Periodic TableConfigurations & The Periodic Table

f blockf block ns2(n-1)d1(n-2)f#, n comes from period

8.12 e8.12 e-- Configurations & The Periodic TableConfigurations & The Periodic Table

f block4f5f

Many exceptions thoughf block ns2(n-1)d1(n-2)f#, n comes from period

8.12 e8.12 e-- Configurations & The Periodic TableConfigurations & The Periodic Table

f blockf block ns2(n-1)d1(n-2)f# n comes from period

4f5f

Note you are notresponsible for knowing filling exceptions in the f block elements

Many exceptions though

8.12 e8.12 e-- Configurations & The Periodic TableConfigurations & The Periodic Table

Write out the electronic configuration for Se?

How many valence electrons does Se have?Se: Z=34 …first we find it on the Table

8.12 e8.12 e-- Configurations & The Periodic TableConfigurations & The Periodic Table

8.12 e8.12 e-- Configurations & The Periodic TableConfigurations & The Periodic Table

Identify the core noble gasconfiguration…[Ar]

Se is in Period 4

8.12 e8.12 e-- Configurations & The Periodic TableConfigurations & The Periodic Table

Identify the core noble gasconfiguration…[Ar]

Se is in Period 4

4s2

8.12 e8.12 e-- Configurations & The Periodic TableConfigurations & The Periodic Table

Identify the core noble gasconfiguration…[Ar]

Se is in Period 4

4s2 3d10

8.12 e8.12 e-- Configurations & The Periodic TableConfigurations & The Periodic Table

Identify the core noble gasconfiguration…[Ar]

Se is in Period 4

4s2 3d10 4p4

1 2 3 4

8.12 e8.12 e-- Configurations & The Periodic TableConfigurations & The Periodic Table

Identify the core noble gasconfiguration…[Ar]

Se is in Period 4

4s2 3d10 4p4

1 2 3 4

This totals 34 e- [Ar] gives 18+2+10+4=34

8.12 e8.12 e-- Configurations & The Periodic TableConfigurations & The Periodic Table

Write out the electronic configuration for Se?

How many valence electrons does Se have?Se: Z=34

Se: [Ar]3d104s24p4

Se: [Ar]3d 4s 4p

8.12 e8.12 e-- Configurations & The Periodic TableConfigurations & The Periodic Table

Write out the electronic configuration for Se?

How many valence electrons does Se have?Se: Z=34

Se: [Ar]3d104s24p4

Se: [Ar]3d 4s 4p

Check: Z=34… 18e-+ 10e-+ 2e-+ 4e- = 34e-

8.12 e8.12 e-- Configurations & The Periodic TableConfigurations & The Periodic Table

Write out the electronic configuration for Se?

How many valence electrons does Se have?Se: Z=34

Se: [Ar]3d104s24p4

Se: [Ar]3d 4s 4p

Valence e- are outer shell (highest n) e-

Answer: 6 valence electrons in Se

8.12 e8.12 e-- Configurations & The Periodic TableConfigurations & The Periodic Table

You could determine this directlyfrom the periodic table as well

Group 16ns2np4

8.12 e8.12 e-- Configurations & The Periodic TableConfigurations & The Periodic Table

What element has the electron configuration

[Ar]3d64s2?

Consult the Periodic Table

8.12 e8.12 e-- Configurations & The Periodic TableConfigurations & The Periodic Table

The science behind “The Simpsons”“Homer goes to College”Come on, Mr. Simpson,

you'll never pass this course if you don't know the Periodic Table.

Ehh, I'll write it on my hand.HO! Including all known

Lanthanides and Actinides? HA HA!! Good Luck.

Note: you will be given the Periodic Table on exams and midterms!

8.12 e8.12 e-- Configurations & The Periodic TableConfigurations & The Periodic Table

Do problems on electron configurations

Attend a tutorial this week

Typical questions…how many valence

electrons…how many unpaired

electrons…what is the electron configuration

of “element name”

9.6 Magnetic Properties9.6 Magnetic Properties

9-6 Magnetic Properties

9.6 Magnetic Properties9.6 Magnetic Properties

Electron configurations affect behavior

of an atom in a magnetic field

9.6 Magnetic Properties9.6 Magnetic Properties

Spinning electron generates magnetic field

Spin Up

Spin Down

For “unpaired” single electron In an orbital…net mag. field or

9.6 Magnetic Properties9.6 Magnetic Properties

Spinning electron generates magnetic field

Spin Up

Spin Down

For “paired” electrons in an orbital…mag. fields cancel

9.6 Magnetic Properties9.6 Magnetic Properties

Diamagnetic atom or ion only has

paired electrons

Magnetic fields are cancelled out

Diamagnetic species are weakly

repelled by an external magnetic field

9.6 Magnetic Properties9.6 Magnetic Properties

Paramagnetic atom or ion has unpaired

electrons

Magnetic fields do not cancel out

Paramagnetic species are attracted

into an external magnetic field

9.6 Magnetic Properties9.6 Magnetic Properties

Determine electron configuration to see

if there are unpaired electrons

Mg [Ne] 3s

Paired electrons…diamagnetic

9.6 Magnetic Properties9.6 Magnetic Properties

Determine electron configuration to see

if there are unpaired electrons

Mg [Ne] 3s

Paired electrons…diamagnetic

Al [Ne] 3s 3p

unpaired electron

9.6 Magnetic Properties9.6 Magnetic Properties

Determine electron configuration to see

if there are unpaired electrons

Mg [Ne] 3s

Paired electrons…diamagnetic

Al [Ne] 3s 3p

unpaired electron…paramagnetic

9.6 Magnetic Properties9.6 Magnetic Properties

Would you expect Cl- to be attracted or

repelled by an external magnetic field?

Cl- [Ar] Paired electrons…Diamagnetic

Answer: Weakly repelled by externalmagnetic field

The OThe O++ ion is ____________.ion is ____________.

1. neutral2. diamagnetic3. It doesn’t exist.4. paramagnetic5. doubly charged

The OThe O++ ion is ____________.ion is ____________.

O: [He]2s22p4

O+: [He]2s22p3

Remember Hund’s rule of maximum

multiplicity.Therefore, 3 unpaired electrons

with parallel spins, i.e. O+ is paramagnetic.

What about O- and O2-?

Chapter 9 The Periodic TableChapter 9 The Periodic Table

The Periodic Table & Some Atomic

Properties

Primo Levi1919-1987

9.1 9.1 Classifying the ElementsClassifying the Elements

9-1 Classifying the Elements: The

Periodic Law & The Periodic Table

9.1 9.1 Classifying the ElementsClassifying the ElementsChemistry before the Periodic Table…messy

“…chemistry just now is enough to drive one mad. It gives me an impression of a primeval tropical forest, full of the most remarkable things, a monstrous and boundless thicket, with no way of escape, into which one may well dread to enter.”Friedrich

Wohler1800-1882

9.1 9.1 Classifying the ElementsClassifying the ElementsUntil Periodic Law proposed by Dimitri

Mendeleev & Lothar Meyer:

“Certain sets of properties recur periodicallywhen the elements are arranged in order of increasing atomic mass”

[Note: modern form uses increasing atomic number (Z)]

9.1 9.1 Classifying the ElementsClassifying the ElementsMendeleev and Meyer noticed patterns

Lothar MeyerGerman

Dimitri MendeleevRussian

9.1 9.1 Classifying the ElementsClassifying the Elements

Dimitri Mendeleev1834-1907

9.1 9.1 Classifying the ElementsClassifying the ElementsMendeleev left blanks in his periodic table

for undiscovered elements.

He predicted the properties the unknown

elements should have.

His predictions were confirmed when the

elements were found (e.g., germanium in 1886).

9.1 9.1 Classifying the ElementsClassifying the ElementsMendeleev predicted the properties for Ge

Germanium is in the same family as Si andthey share similar properties

9.1 9.1 Classifying the ElementsClassifying the ElementsMendeleev’s Table used atomic mass values

Blank(Germanium)

Mendeleev predictedproperties like Si

Germanium is in the same family as Si andthey share similar properties…powerful tool

9.1 9.1 Classifying the ElementsClassifying the ElementsModern Periodic Table: arrange according to

atomic number (Z)

9.1 9.1 Classifying the ElementsClassifying the ElementsGroups run down…Periods run across Table

Period 3

Group 14

Mohammed Abubakr, Hyderabad, IndiaMohammed Abubakr, Hyderabad, India

The Biochemical Periodic TableThe Biochemical Periodic Table

Yoshiteru Maeno at Kyoto University

bricks are the number of valence electrons for the neutral form of that element (main group

LEGO

9.2 9.2 Metals Nonmetals & their IonsMetals Nonmetals & their Ions

9-2 Metals & Nonmetals & Their Ions

Platinum

Sulfur

9.2 9.2 Metals Nonmetals & their IonsMetals Nonmetals & their IonsMake predictions based on e- configurations

Metals Non Metals

Noblegases

9.2 9.2 Metals Nonmetals & their IonsMetals Nonmetals & their IonsMetals tend to give up electrons

Metals

9.2 9.2 Metals Nonmetals & their IonsMetals Nonmetals & their IonsNonmetals tend to gain electrons

Non Metals

9.2 9.2 Metals Nonmetals & their IonsMetals Nonmetals & their IonsNoble gases neither gain nor lose e-

Noblegases

9.2 9.2 Metals Nonmetals & their IonsMetals Nonmetals & their IonsRecall noble gas configuration ns2np6

Noblegases

*

9.2 9.2 Metals Nonmetals & their IonsMetals Nonmetals & their IonsNoble gases: complete octet ns2np6

Eight valence electrons: complete shell

Noble gas configuration is very stable

4s 4p[Ar]3d104s24p6

Metals lose electrons to achieve ns2np6 stabilityNonmetals gain electrons to achieve ns2np6

stability

Kr (Z=36) [Ar]3d10

9.2 9.2 Metals Nonmetals & their IonsMetals Nonmetals & their IonsMetals tend to lose electrons

39.098K19

[Ar]4s1

9.2 9.2 Metals Nonmetals & their IonsMetals Nonmetals & their IonsMetals tend to lose electrons

[Ar]4s1

K K+ + 1e-

[Ar]

Noble gasconfigurationfor the cation

9.2 9.2 Metals Nonmetals & their IonsMetals Nonmetals & their IonsMetals tend to lose electrons

137.33Ba56

[Xe]6s2

9.2 9.2 Metals Nonmetals & their IonsMetals Nonmetals & their IonsMetals tend to lose electrons

[Xe]6s2

Ba Ba2+ + 2e-

[Xe]

Noble gasconfigurationfor the cation

9.2 9.2 Metals Nonmetals & their IonsMetals Nonmetals & their IonsNonmetals tend to gain electrons

79.904Br35

[Ar]3d104s24p5

9.2 9.2 Metals Nonmetals & their IonsMetals Nonmetals & their IonsNonmetals tend to gain electrons

[Ar]3d104s24p5

Br -Br + 1e-

[Ar]3d104s24p6 = [Kr]

Noble gasconfigurationfor the anion

Kryptonite

9.2 9.2 Metals Nonmetals & their IonsMetals Nonmetals & their IonsNonmetals tend to gain electrons

32.06S16

[Ne]3s23p4

9.2 9.2 Metals Nonmetals & their IonsMetals Nonmetals & their IonsNonmetals tend to gain electrons

[Ne]3s23p4

S2-S + 2e-

[Ne]3s23p6 = [Ar]

Noble gasconfigurationfor the anion

9.2 9.2 Metals Nonmetals & their IonsMetals Nonmetals & their IonsTransition metal ions also lose electrons

47.88Ti22

[Ar]3d24s2

9.2 9.2 Metals Nonmetals & their IonsMetals Nonmetals & their IonsTransition metals also tend to lose electrons

Ti Ti2+ + 2e-

[Ar]3d24s2 [Ar]3d2

Note: Electronsare lost fromthe outermost orbital(not the last one filled)

9.2 9.2 Metals Nonmetals & their IonsMetals Nonmetals & their IonsTransition metal ions can achieve noble gas

configuration e.g., Ti4+

Ti Ti2+ + 2e-

[Ar]3d24s2 [Ar]3d2

Ti Ti4+ + 4e-

[Ar]3d24s2 [Ar]

Noble gas configuration

9.2 9.2 Metals Nonmetals & their IonsMetals Nonmetals & their IonsMost transition metal ions do not achieve

noble gas configuration e.g. Fe2+, Fe3+

Fe Fe2+ + 2e-

[Ar]3d64s2 [Ar]3d6

Fe Fe3+ + 3e-

[Ar]3d64s2 [Ar]3d5

9.2 9.2 Metals Nonmetals & their IonsMetals Nonmetals & their Ions

Which would you expect to be more stable

Fe2+ or Fe3+?

9.2 9.2 Metals Nonmetals & their IonsMetals Nonmetals & their Ions

Which would you expect to be more stable

Fe2+ or Fe3+?

Answer: Fe3+

9.2 9.2 Metals Nonmetals & their IonsMetals Nonmetals & their Ions

Which would you expect to be more stable

Fe2+ or Fe3+?

Answer: Fe3+

Why? Extra stability associated with a

half-filled 3d shell.

Fe2O3

Fe3+

9.2 9.2 Metals Nonmetals & their IonsMetals Nonmetals & their IonsMost transition metal ions do not achieve

noble gas configuration

Cu Cu+ + 1e-

[Ar]3d104s1 [Ar]3d10 = [Ne]3s23p63d10

Pseudo noble gasconfiguration18e- in outer shell

9.3 9.3 The Sizes of Atoms & IonsThe Sizes of Atoms & Ions

9-3 The Sizes of Atoms & Ions

9.3 9.3 The Sizes of Atoms & IonsThe Sizes of Atoms & IonsThere are size trends for atoms and ions

9.3 9.3 The Sizes of Atoms & IonsThe Sizes of Atoms & IonsHow do we define atomic, ionic radius?

Electron probability cloud…border uncertain

We can determine internuclear distances

We define radii based on distance between

two nuclei

9.3 9.3 The Sizes of Atoms & IonsThe Sizes of Atoms & IonsCovalent Radius (for covalent bonded atoms)

r r

Internuclear distance is2 x atomic radius(same species)

O2 (oxygen molecule)

2r = 143 pm

So r = 71.5 pm

18931893Windsor,Windsor,OntarioOntario

9.3 9.3 The Sizes of Atoms & IonsThe Sizes of Atoms & IonsIonic Radius (for ionic bonded species)

Internuclear distance issum of the two radii

Na+Cl- (ionic compound)

rNa+ + rCl- = 280 pmInternuclear dist.

rNa+99pm

Na+ Cl-

If you know rNa+…you can calculate rCl-

rCl-181pm

9.3 9.3 The Sizes of Atoms & IonsThe Sizes of Atoms & IonsMetallic Radius (for metal atoms in crystal)

Crystalline Solid MetalAg Ag

Internuclear distance is2 x metallic radius

(same species)

2r = 288 pmSo r = 144 pm

r r

2r

9.3 9.3 The Sizes of Atoms & IonsThe Sizes of Atoms & IonsWhat are the radii of Li+ and of I-?

a=600pm

c2 = a2 + a2 = 2a2 = 2(600pm)2 (Pythagorean)c = 849 pm = 4rI-

c

ca

a

r -r -

r -r -

rI- = 212 pm

r -

r -

2r+

a = 2rI- + 2rLi+

600pm=2*212pm+2rLi+

rLi+ = 88 pm

9.3 9.3 The Sizes of Atoms & IonsThe Sizes of Atoms & IonsThe ions in crystalline LiI are arranged as

shown below. If a = 600pm, what is the

radius of Li+? What is the radius of I-?

a=600pm

I-

Li+

rI- = 212pm

rLi+ = 88pm

8.10 Multielectron Atoms8.10 Multielectron AtomsElectron Screening

Inner shellelectronsscreenouter e-

from fullattraction ofthe nucleus

Outer e-

experiencea lowereffective nuclearcharge

Zeff < ZZeff = Z - S

where S is charge that is screened

8.10 Multielectron Atoms8.10 Multielectron Atomss orbitals are better at screening than p & d

s orbitals > p orbitals > d orbitalss Zeff > p Zeff > d Zeff

Valence electrons will shield each other to aMuch Smaller degree than inner shell electrons

Orbital energy depends on n and Zeff

Screeningstrength(for same n)

2H

2eff

n nhcRZ- E =

9.3 9.3 The Sizes of Atoms & IonsThe Sizes of Atoms & Ions

Atomic Number

AtomicRadius(pm)

Can we explain the size trends?

9.3 9.3 The Sizes of Atoms & IonsThe Sizes of Atoms & Ions

Atomic Number

AtomicRadius(pm)

Atomic radius usually decreases fromleft to right across a period in s & p blocks

8.12 e8.12 e-- Configurations & The Periodic TableConfigurations & The Periodic Table

s block

Filling nsorbitals

Filling nporbitals

p block

Putting in valence electronsSo, S ∼ constant while Z increasesZeff increases and radius decreases

rr

9.3 9.3 The Sizes of Atoms & IonsThe Sizes of Atoms & Ions

Atomic Number

AtomicRadius(pm)

Atomic radius usually increasesfrom top to bottom down a group

9.3 9.3 The Sizes of Atoms & IonsThe Sizes of Atoms & IonsThere are size trends for atoms and ions

Increasing n down agroup…orbitals get larger

so radius increases

r

9.3 9.3 The Sizes of Atoms & IonsThe Sizes of Atoms & Ions

Atomic Number

AtomicRadius(pm)

Atomic radius often stays relatively constantacross a period for transition metals

8.12 e8.12 e-- Configurations & The Periodic TableConfigurations & The Periodic Table

d blockTransition metals

Filling (n-1)dorbitals

Putting electrons in an inner shellSo, S increases as Z increasesZeff ∼ constant and radius ∼ constant

r ∼ const.

9.3 9.3 The Sizes of Atoms & IonsThe Sizes of Atoms & IonsRefer to the periodic table and arrange N, O,

and P in order of increasing atomic radius

9.3 9.3 The Sizes of Atoms & IonsThe Sizes of Atoms & Ions 9.3 9.3 The Sizes of Atoms & IonsThe Sizes of Atoms & Ions

For main group atomsradius decreases across a period

9.3 9.3 The Sizes of Atoms & IonsThe Sizes of Atoms & Ions

For main group atomsradius decreases across a period

Predict O < N

9.3 9.3 The Sizes of Atoms & IonsThe Sizes of Atoms & Ions

For main group atomsRadius decreases across a period

Predict O < N

Atomic radius increases down a group

9.3 9.3 The Sizes of Atoms & IonsThe Sizes of Atoms & Ions

For main group atomsradius decreases across a period

Predict O < N < P

Atomic radius increases down a group

9.3 9.3 The Sizes of Atoms & IonsThe Sizes of Atoms & IonsRefer to the periodic table and arrange N, O,

and P in order of increasing atomic radius

Predicted: O < N < PActual: 73pm 75pm 110pm

9.3 9.3 The Sizes of Atoms & IonsThe Sizes of Atoms & IonsCations are smaller than the parent atoms

Cations…lose electron(s)…Z stays constant

Na

r = 186 pm r = 99 pm

+ 1e-Na+

9.3 9.3 The Sizes of Atoms & IonsThe Sizes of Atoms & IonsAnions are larger than the parent atoms

Anion…gain electron(s)…Z stays constant

Cl-

Cl

r = 99 pm r = 181 pm

+ 1e-

9.3 9.3 The Sizes of Atoms & IonsThe Sizes of Atoms & IonsFor isoelectronic cations…the more positive

charge…the smaller the ionic radius

Na+ Mg2+

r = 99 pm r = 72 pm

Na+ 1s22s22p6

Z=11Mg2+ 1s22s22p6

Z=12isoelectronic

9.3 9.3 The Sizes of Atoms & IonsThe Sizes of Atoms & IonsFor isoelectronic anions…the more negative

charge…the larger the ionic radiusCl- [Ne]3s23p6

Z=17P3- [Ne]3s23p6

Z=15isoelectronic

Cl-

r = 181 pm

P3-

r = 212 pm

9.3 9.3 The Sizes of Atoms & IonsThe Sizes of Atoms & IonsRefer to the periodic table and arrange these

species in order of increasing size: Na+,

Mg2+, O2-, F-, Ne

9.3 9.3 The Sizes of Atoms & IonsThe Sizes of Atoms & IonsDetermine e- configurations from table

All species have [Ne] configuration

Na+Mg2+O2-F-Ne

For isoelectric configurations radius will increasewith decreasing Z

9.3 9.3 The Sizes of Atoms & IonsThe Sizes of Atoms & IonsRefer to the periodic table and arrange these

species in order of increasing size: Na+,

Mg2+, O2-, F-, Ne

Mg2+ < Na+ < Ne < F- < O2-

Z=12 11 10 9 8

Answer:

Increasing radiusActual: 72pm 99pm 71pm 133pm 140pm

?

9.4 Ionization Energy9.4 Ionization Energy

9-4 Ionization Energy

e-

Energy required to strip an electronfrom a gaseous state atom (or ion)

ΔEIE = ?

9.4 Ionization Energy9.4 Ionization Energy

Ionization energy for H-like species

n=1

n=2

n=3n=4n=5n=∞

hνAtom absorbsphotonΔEIE=hν

E

2H

2

IE 1hcRZ E =Δ

H-like speciesOnly one electron

From ground state

9.4 Ionization Energy9.4 Ionization Energy

Definition

e-

Energy required to strip an electronfrom a gaseous state atom (or ion)

Not spontaneous…requires energy input

Ionization Energy = I

9.4 Ionization Energy9.4 Ionization Energy

In = nth Ionization energy...remove nth e-

Al(g) Al+(g) + 1e-

Al+(g) Al2+(g) + 1e-

I1=577.6 kJ/mol

I2=1,817 kJ/mol

Al2+(g) Al3+

(g) + 1e- I3=2,745 kJ/mol

Al3+(g) Al4+

(g) + 1e- I4=11,580 kJ/mol

[Ne] noble gas configuration…extra stable

9.4 Ionization Energy9.4 Ionization Energy

I depends on Zeff and n

2H

2eff

nhcRZ I =

Larger Zeff…higher I…e- held more tightly

Higher n…lower I…outer e- held less tightly

22eff n

1 I and Z I ∝∝

9.4 Ionization Energy9.4 Ionization Energy

I 1kJ

/mol

Atomic No. (Z)

Periodic Trends for II generally increases across a period

I increases as Zeff increases across a period

8.12 e8.12 e-- Configurations & The Periodic TableConfigurations & The Periodic Table

s block

Filling nsorbitals

Filling nporbitals

p block

Putting in valence electronsSo, S ∼ constant while Z increasesZeff increases

II

9.4 Ionization Energy9.4 Ionization Energy

I 1kJ

/mol

Atomic No. (Z)

Periodic Trends for II generally decreases down a group

I decreases as n increases down a group

9.4 Ionization Energy9.4 Ionization Energy

There are IE trends

I

9.4 Ionization Energy9.4 Ionization Energy

There are IE trends

n

Zeff increasesonly slightlydown a group

I

9.4 Ionization Energy9.4 Ionization Energy

There are some exceptions

9.3 9.3 The Sizes of Atoms & IonsThe Sizes of Atoms & IonsWe would predict I1 Mg < I1 Al

9.4 Ionization Energy9.4 Ionization Energy

There are some exceptions

I1 = 737.7 kJ/mol Mg

I1 = 577.6 kJ/mol Al

Why lower?

Mg [Ne]3s2

Al [Ne]3s23p1

Easier to pull the electron from a higherenergy p orbital thana lower energy s orbital

Al is lower???

9.4 Ionization Energy9.4 Ionization Energy

Remember that electrons are ionized from

the orbital with the highest n

This is not necessarily the last orbital to be

filled

If there are different types of orbitals with the

same n, the e- is ionized from the highest

energy orbital

9.4 Ionization Energy9.4 Ionization Energy

Remember that electrons are ionized from

the orbital with the highest n

This is not necessarily the last orbital to be

filled

If there are different types of orbitals with the

same n, the e- is ionized from the highest

energy orbital

Lower energy s < p < d Higher energy

9.4 Ionization Energy9.4 Ionization Energy

Example

Sc [Ar]3d14s2

Last e- added

First e- removed

Sc [Ar]3d14s2 Sc+ [Ar]3d14s1 + 1e-

Sc+ [Ar]3d14s1 Sc2+ [Ar]3d1 + 1e-

Sc2+ [Ar]3d1 Sc3+ [Ar] + 1e-

9.4 Ionization Energy9.4 Ionization Energy

Typical problems…refer to the periodic table

and arrange elements in expected order of

increasing first ionization energy I1

Attend tutorials for examples

9.5 Electron Affinity9.5 Electron Affinity

9-5 Electron Affinity

e-

Energy change when an electron is addedto a gaseous state atom (or ion)

ΔEEA = ?

9.5 Electron Affinity9.5 Electron Affinity

Definition

e-

Energy change when an electron is addedto a gaseous state atom (or ion)

Electron Affinity = EA

9.5 Electron Affinity9.5 Electron Affinity

EA is often negative

This means energy is given off

(exothermic)

Note that ionization energy was always

positive…it required input of energy

9.5 Electron Affinity9.5 Electron Affinity

F(g) + 1e- F-(g) EA=-328 kJ/mol

1s22s22p5 1s22s22p6

9.5 Electron Affinity9.5 Electron Affinity

EAn = nth Electron Affinity...add nth e-

O(g) + 1e- O-(g) EA1=-141.0 kJ/mol

O-(g) + 1e- O2-

(g) EA2=+744 kJ/mol

Positive because it ishard to add a second electron due to repulsion

9.5 Electron Affinity9.5 Electron Affinity

Electron affinity trends are harder to

discern

It is easy to get confused!

A high affinity for electrons means a

large negative electron affinity

9.5 Electron Affinity9.5 Electron AffinityEA tends to become less negative (lower affinity)down a Group

9.5 Electron Affinity9.5 Electron Affinity

Highest affinities (most negative EA)are found in Group 17

9.5 Electron Affinity9.5 Electron Affinity

Highest EA values are found ingroup 17…ns2np5…readily gain one e-

9.7 Periodic Properties of the Elements9.7 Periodic Properties of the Elements

9-7 Periodic Properties of the Elements

9.7 Periodic Properties of the Elements9.7 Periodic Properties of the Elements

Summary of Atomic Properties Fig.9.11

Arrowsindicateincreasing

9.7 Periodic Properties of the Elements9.7 Periodic Properties of the Elements

Summary of Atomic Properties Fig.9.11EA becomes more negative

Arrowsindicateincreasing

9.7 Periodic Properties of the Elements9.7 Periodic Properties of the Elements

Summary of Atomic Properties Fig.9.11EA becomes more negative

We can understand the trends in terms ofZeff (screening); n (orbital size); e- repulsion

Arrowsindicateincreasing

9.7 Periodic Properties of the Elements9.7 Periodic Properties of the Elements

Periodicity…Predict Properties Physicalpropertiesoftenchangeuniformlydown agroup

e.g., melting &boilingpoints

9.7 Periodic Properties of the Elements9.7 Periodic Properties of the Elements

Periodicity…Predict Properties

9.7 Periodic Properties of the Elements9.7 Periodic Properties of the Elements

Periodicity…Predict Properties Halogensdiatomice.g.,Cl2Br2I2

9.7 Periodic Properties of the Elements9.7 Periodic Properties of the Elements

Periodicity…Predict Properties

Can we predict the melting point of Br2?Estimated mp = (172K+387K)/2 = 280K

Actual mp for Br2 = 266KNot

Too bad!

Table 9.5

9.7 Periodic Properties of the Elements9.7 Periodic Properties of the Elements

Periodicity…Predict Properties

Try predicting the boiling point of Br2 by averaging

Example 9-5 pg. 360

Table 9.5

9.7 Periodic Properties of the Elements9.7 Periodic Properties of the Elements

As you learn reactions you will see trendsLEO the lion says GER

LEO = loss of electrons Oxidation GER = gain of electrons Reduction

9.7 Periodic Properties of the Elements9.7 Periodic Properties of the Elements

As you learn reactions you will see trendsGroups 1 & 2Metals…lose e-

e- loss is OxidationGroup 1 & 2 Metalsare generallygood “reducing agents”A reducing agent undergoesoxidation…but drives reduction (gainof e- by another species)

9.7 Periodic Properties of the Elements9.7 Periodic Properties of the Elements

As you learn reactions you will see trends

Group 17Nonmetals…gain e-

They undergo reduction(gain of electrons)

They act as oxidizing agents

9.7 Periodic Properties of the Elements9.7 Periodic Properties of the Elements

As you learn reactions you will see trends

Group 17Nonmetals…gain e-

They undergo reduction(gain of electrons)

They act as oxidizing agents(they are reduced but driveoxidation in another species)

9.7 Periodic Properties of the Elements9.7 Periodic Properties of the Elements

In Science, we use models to predict & we

test the predictions

Periodic Tableis central forunderstanding Chemistry