1chemistry 2c lecture 6: april 12 th, 2006 lecture 6:transition metals corrosion- unwanted oxidation...

1Chemistry 2C Lecture 6: April 12th, 2006

Lecture 6:Transition Metals

• Corrosion- unwanted oxidation of material (e.g. rust with Fe)

• Cathodic Protection (sacrificial metals)• Electrolysis (of water)

• Electroplating

I. MetallurgyII. Electronic Configuration

III. Transition Metal properties


Metallurgy

In chapter 24, we will ignore metallurgy (24.2 & 24.3). Read it for fun as they deal with how metals are extracted from their natural

sources. But, let’s talk about occurrence of metal in a general sense.

Almost all metals are founded in combined form in nature. If not, we say they are in the “native form.” Au, Ag, and Pt are the main ones otherwise, the metals are found in minerals (usually oxides, sulfides

or silicates).

Hematite: Fe2O3 Galena: PbS Sphalerite: ZnS

http://mineral.galleries.com/minerals/


Ores refer to concentrated deposits that have commercial value

Recovering metals from these ores is the science of metallurgy and involve several steps, specific to the metal that you are extracting, the purity of the product or whether an alloy is

produced

Manganese Ore Lead Ore Gold Ore

Metallurgy


Alloys are metallic materials containing two or more metals

Alloys are usually designed to have properties that are more desirable than those of their components. For instance, steel is

stronger than iron, one of its main elements.

An amalgam is any alloy of mercury. Most metals are soluble in mercury, but some (such as iron) are not. Amalgams are commonly used in dental

fillings.

Dental fillings: Ag/Sn/Cu/Hg

14 Carat Gold: Cu/Au

24 Carat Gold: Pure Au, but too soft for rings and other jewelry

Metallurgy


Transition Metals Facts

Many of the most important metals in modern society are the transition metals

In the periodic table, they comprise of more

than half of the elements.


Transition Metals FactsWhere are they:

The s block elements - Groups 1 & 2 (1A-2A)The p block elements- Groups 13-18 (3A-

8A)The d block elements - Groups 3-12 (3B-1B)The f block elements



Electronic configurations for noble gases

[He] 1s2

[Ne] 1s2 2s2 2p6

[Ar] 1s2 2s2 2p6 3s2 3p6

In multi-electron atoms (not Hydrogenic atoms), the orbital energies are like this

(qualitative)

1s

2s

2p 2p 2p

3s

3p 3p 3p

4s

3d 3d 3d

Energ

y

3d3d

4p 4p 4p

Each box is an orbital (can hold 2 e-)

Within each sub-shell, the orbitals are degenerate (same energy)

•The three p oribals are degenerate•The five d-orbiatal are degenerate



n, l, ml, ms

n Principle quantum number

l angular momentum QNml magnetic QNms spin QN

Recall the Pauli exclusion principle:No two electrons in an atom can have the same set of four quantum

numbers

3d 3d 3d 3d3d

For the 3d orbitalsn=3l=2

ml= -2, -1, 0, 1, 2Ms= ½ or -½

Orbitals can hold a max of 2 electrons and they must be of opposite spin: So there are 2x5 elements for each row of

d-block Transition metals


Electronic configurationAfter Ar, things get more interesting, complex, and even cool!

Can simplify the electronic configuration by using the configuration of the closest noble gas configuration (e.g. Ar)

[Ar]: 1s2 2s2 2p6 3s2 3p6

[K]: 1s2 2s2 2p6 3s2 3p6 4s1

[Ca]: 1s2 2s2 2p6 3s2 3p6 4s2

Now we start to fill in the d-orbitals

[Sc]: 1s2 2s2 2p6 3s2 3p6 4s2 3d1

d-oribitals

[Sc]: [Ar] 4s2 3d1


Electronic configurationOrbitals are filled according to Hund’s rule – unpaired electrons first before

putting two electrons in a single orbital

[Mn]: [Ar] 4s2 3d5 ↑↓

↑ ↑ ↑ ↑↑

4s 3sAll five d electrons are unpaired and occupy separate orbitals


Electronic configurationOrbitals are filled according to Hund’s rule – unpaired electrons first before

putting two electrons in a single orbital

[Co]: [Ar] 4s2 3d7 ↑↓

↑↓

↑ ↑ ↑↑↓

4s 3s

Now two d-oribtals are occupied with two electrons (ms= ½ and ms= -½)


Electronic configurationAfter the d orbitals are filled, the 4p orbitsal will start to be filled starting

with Ga and continuing until Kr

[Kr]: [Ar] 4s2 3d10 4p6 ↑↓

↑↓

↑↓

↑↓

↑↓

↑↓

4s 3s

The same pattern occurs in the next row, so that the 5s is filled before 4d, which is

then filled before 5p

↑↓

↑↓

↑↓

4p


Rare Earth Transition Metals

After the 6s, there is a break and the then start to fill the 4f orbitals

Lanthanide Elements

Actinide Elements


Rare Earth Transition Metals

The 4f and the 5d energies are close, so there is some mixing with the d-block metals, but mostly the order is: 6s, 4f, 5d, 6p

[La]: [Xe] 6s2 5d1

[Ce]: [Xe] 6s2 4f2

Table D in the text book (pg. A17)

The first two lanthanides

Actinides: Rare and radioactive and will be discussed later


Transition Metals

So, the transition elements” term refers to the d-block and also the f-block elements. The name also refers to their intermediate properties between

the very reactive s-block and less reactive p-block metals


Transition Metals PropertiesTransition metals are all metals which means:1) Clean metallic surface has a characteristic luster

2) Conduct heat well (flow of thermal energy)3) Conduct electricity (flow of electrons)

4) Most are malleable (can be hammered)5) Most are ductile (can be drawn in a wire

Most TS have high melting points except Zn, Cd, Hg (weaker metallic bonding)

e.g. V, 1917◦Ce.g. Zn, 420◦C

Atomic radius (result from the combination of several factors)1) As nuclear charge ↑ and electrons ↑, the effective nuclear charge

exerts a greater pull on the valence electrons and they are pulled in close; thus atomic radii decrease in going from Left to Right in a row

2) However, electrons in the d-subshell tend to experience repulsive effects and expand the radius


Transition Metals Radii

21 [Sc] [Ar] 4s2 3d1 161 pm

22 [Ti] [Ar] 4s2 3d2 145 pm23 [V] [Ar] 4s2 3d3 132 pm24 [Cr] [Ar] 4s1 3d5 125 pm25 [Mn] [Ar] 4s2 3d5 124 pm26 [Fe] [Ar] 4s2 3d6 124 pm27 [Co] [Ar] 4s2 3d7 125 pm28 [Ni] [Ar] 4s2 3d8 125 pm29 [Cu] [Ar] 4s1 3d10 128 pm30 [Zn] [Ar] 4s2 3d10 133 pm

Z (nuclear charge) Metals Electronic ConfigurationMetallic Radius

100 pm=1Å

Special stability of half filled shells results in extra energy required to

pair electrons

1chemistry 2c lecture 6: april 12 th, 2006 lecture 6:transition metals corrosion- unwanted oxidation...

Documents