Chm361_chapter 4 Transition Metals.pdf

CHM361 CHAPTER 5: TRANSITION METAL

CONTENTS Introduction on Transition Metals

Electron Configuration of Atoms and Ions

Physical and Chemical Properties of Transition Metals (First Row of Transition Metals)

Extraction and Industrial Applications of Iron

LEARNING OUTCOMES

Upon completion of this chapter, students will be able to:

Apply the knowledge of electron configuration of transition metals and ligand structures to name and determine the geometry, isomerism and hybridization of coordination compounds.

Conduct, observe and report scientific investigation in selected areas of inorganic and coordination chemistry.

INTRODUCTION Transition elements are the element with the partially-filled d orbitals. (Zn, Cd & Hg are not considered as transition element because do not have this characteristic)

Also known as the d-block elements.

Found in the fourth row of the periodic table.

Located in groups 3 through 11.

They are called transition metals because they transition between the highly reactive s block metals and the much less reactive metals of group 12 and the p

ELECTRON CONFIGURATION OF ATOMS & IONS 3d orbital are filled after the 4s orbital is fully occupied by electrons.

The filling of electrons in d-orbitals follows the same rules discussed earlier. Ti = 22 ↑ ↓

↑ ↓

1s

↑ ↓

2s

↑ ↓

↑ ↓

2p

↑ ↓

↑ ↓

3s

↑ ↓

↑ ↓

3p

↑ ↓

↑

↑

4s

3d

Fe = 26 ↑ ↓ 1s

↑ ↓ 2s

↑ ↓

↑ ↓ 2p

↑ ↓

↑ ↓ 3s

↑ ↓

↑ ↓ 3p

↑ ↓

↑ ↓ 4s

↑ ↓

↑

↑ 3d

↑

↑

4s orbital which will fill first, followed by all the 3d orbitals. the 4s orbital behaves as the outermost, highest energy orbital.

ELECTRON CONFIGURATION OF ATOMS & IONS In terms of energy, the 4s has lower energy than the 3d orbital.

But as soon as the electrons occupy the 3d orbital, the 4s repelled to a higher energy.

Therefore, it can be written as: Ti22 : 1s2 2s2 2p6 3s2 3p6 4s2 3d2

By applying Afbau principle

Ti22 : 1s2 2s2 2p6 3s2 3p6 3d2 4s2

Due to energy level after repulsion

ELECTRON CONFIGURATION OF ATOMS & IONS When transition metals form simple ions, the electrons are removed from the orbital of the highest energy first.

The electrons from 4s orbital are removed first before the electrons in 3d orbitals.

Fe26 : 1s2 2s2 2p6 3s2 3p6 3d6 4s2

Fe2+ : 1s2 2s2 2p6 3s2 3p6 3d6 Fe3+ : 1s2 2s2 2p6 3s2 3p6 3d5

ELECTRON CONFIGURATION OF ATOMS & IONS Chromium & Copper are the two transition element that show irregularities in electronic configuration. To achieve stability, the electronic configuration is preferred to have filled or half-filled orbital.

ELECTRON CONFIGURATION OF ATOMS & IONS Expected electronic configuration: Cr24

↑ ↓ 1s

↑ ↓

↑ ↓

2s

↑ ↓

↑ ↓

2p

↑ ↓

↑ ↓

3s

↑ ↓

↑ ↓

3p

↑ ↓

↑

↑

4s

↑

↑

3d

Cr24 : 1s2 2s2 2p6 3s2 3p6 3d2 4s2

one electrons from 4s orbital occupies 3d orbital to have half-filled orbital arrangement. ↑ ↓ 1s

↑ ↓ 2s

↑ ↓

↑ ↓

↑ ↓

2p

Cr24 : 1s2 2s2 2p6 3s2 3p6 3d5 4s1

↑ ↓ 3s

↑ ↓

↑ ↓ 3p

↑ ↓

↑ 4s

↑

↑

↑ 3d

↑

↑

ELECTRON CONFIGURATION OF ATOMS & IONS Expected electronic configuration: Cu29

↑ ↓ 1s

↑ ↓

↑ ↓

2s

↑ ↓

↑ ↓

2p

↑ ↓

↑ ↓

3s

↑ ↓

↑ ↓

3p

↑ ↓

↑ ↓

↑ ↓

4s

↑ ↓

↑ ↓

↑

3d

Cu29 : 1s2 2s2 2p6 3s2 3p6 3d9 4s2

one electrons from 4s orbital occupies 3d orbital to have half-filled orbital arrangement. ↑ ↓ 1s

↑ ↓ 2s

↑ ↓

↑ ↓

↑ ↓

2p

Cu29 : 1s2 2s2 2p6 3s2 3p6 3d10 4s1

↑ ↓ 3s

↑ ↓

↑ ↓ 3p

↑ ↓

↑ 4s

↑ ↓

↑ ↓

↑ ↓ 3d

↑ ↓

↑ ↓

ELECTRON CONFIGURATION OF ATOMS & IONS Ar Inner core configuration : [Ar]18 = 1s22s22p63s23p6 ELEMENT

ELECTRONIC CONFIGURATION

ABBREVIATED EC

Sc21

1s22s22p63s23p63d14s2

[Ar]3d14s2

Ti22

1s22s22p63s23p63d24s2

[Ar]3d24s2

V23

1s22s22p63s23p63d34s2

[Ar]3d34s2

Cr24

Mn25 Fe26 Co27 Ni28 Cu29 Zn30

TRY THIS Write the subshell electron configurations for: 3+ a) Cr b)

Mn4+

c)

Fe2+

d)

Fe3+

e)

Co2+

TREND ACROSS THE PERIOD OF PERIODIC TABLE ATOMIC SIZE



Decrease at first, then remains relatively constant.



additional electrons are added to the inner 3d atomic orbitals resulting in stronger attraction to the nucleus.



3d electrons shield the outer 4s electrons from the increasing number of protons in the nucleus.

TREND DOWN THE GROUP OF PERIODIC TABLE ATOMIC SIZE

Atomic size increases from Period 4 to 5 Total number of shells increase and orbitals get larger leading to greater size.

Atomic size for Period 5 to 6 almost the same size . 

The third row of transition metals contains many more protons in their nuclei.



The third row "contracts" because of these additional protons. This effect is called the “lanthanide contraction”.

TREND ACROSS THE PERIOD OF PERIODIC TABLE IONIZATION ENERGY Amount of energy required to remove an electron from its ground state.



Increase relatively little across the transition metals of a particular period.



Across the period, atomic size decreasing so electrons are more closely attracted to the nucleus, thus the electron is more difficult to be removed.

TREND DOWN THE GROUP OF PERIODIC TABLE IONIZATION ENERGY

Generally increases moving down a group. Because of two factors: Relatively small increase in size combined with relatively large increase in nuclear charge. As the element going down the group, there are just small increasing in size and the nuclear charge increase. Atom with higher nuclear charge held electrons closely to the nucleus. Therefore, ionization energy increase. Counter to the pattern in the main groups.

TREND ACROSS THE PERIOD OF PERIODIC TABLE ELECTRONEGATIVITY 

ability of an atom to attract the bonding electrons to itself.

Increase relatively little across the transition metals of a particular period.

Crossing the period, atomic size decrease. The smaller the atomic size, the higher the ability to attract bonding to itself.

TREND DOWN THE GROUP OF PERIODIC TABLE ELECTRONEGATIVITY

Increase within a group from Period 4 to 5, then generally remains unchanged from Period 5 to 6.

-

Down the group, atomic mass increase. The heavier elements often have high EN values.

SPECIAL CHARACTERISTIC OF TRANSITION ELEMENT

Variable Oxidation States

Complex Ion

UNIQUENESS

Coloured Compounds

Catalytic Properties

Va riab e Oxidati on tate s l S Sc

V

Cr

Ti

+3

Fe

Co

Ni

Cu

Zn

Mn +1

+1

+2

+2

+2

+2

+2

+2

+2

+2

+3

+3

+3

+3

+3

+3

+3

+3

+4

+4

+4

+4

+5

+5

+5

+6

+6

+4

+2

Variable Oxidation States oxidation state arises from the loss of the 4s and 3d electrons. All transition metals exhibit a +2 oxidation state (electrons are first removed from the 4s sub-shell). This is because the electrons in the d shell are closer to the nucleus than the atoms in the s shell. As a result, the electrons in the highest s shell tend to be lost first, rather than the electrons in the d shell.

since transition metals have 5 d-orbitals which d-orbital has a variety of oxidation states. The d electrons are fairly easy to remove, but there are certain states that are more stable than others. The half-full set of 'd' orbitals is spherically symmetrical and has an extra degree of stability.

Variable Oxidation States Increase in the number of oxidation states from Sc to Mn because of the unpaired electrons increases. This is because, unpaired valence electrons are unstable and eager to bond with other chemical species.

Decrease in the number of oxidation states from Mn to Zn, due to the pairing of d electrons occurs after Mn.

COLOURED COMPOUND Colors can vary depending on the charge, number & groups of atom attach to the metal ion (ligands).

When ligands are present, some d orbitals become higher / lower energy than before.

When the d-level is not completely filled, it is possible to promote electron from a lower energy d-orbital to a higher energy d orbital by absorption of a photon of electromagnetic radiation (d-d transitions).

The wavelength of the light absorbed is affected by the size of the energy gap between the d orbitals.

COMPLEX ION A complex ion has a transition metal ion at its centre with a number of ligands surrounding it.

Ligands have active lone pairs of electrons which used to form coordinate bonds with the metal ion.

Other metals also form complex ions - it isn't something that only transition metals do. However, transition metal form a very wide range of complex ions.

CATALYTIC PROPERTIES Transition metals and their compounds are often good catalysts.

Transition metals and their compounds function as catalysts either because of their ability to change oxidation state or, in the case of the metals, to adsorb other substances on to their surface and activate them in the process.

CATALYTIC PROPERTIES Hydrogenation (Reduction) Ni CH2=CH2(g) + H2(g) →

CH3-CH3(g)

The Haber Process

Formation of ammonia from nitrogen and hydrogen using iron as the catalyst. Fe

N2(g) + 3H2(g) →

2NH3(g)

EXTRACTION OF IRON Iron is found in nature in form of its oxides, carbonates and sulphates.

The main ores are:  Haematite (Fe2O3)  Magnetite (Fe3O4)  Iron

Pyrites (FeS2)

Iron ore contain impurities.

Iron ore is reduced to iron metal by heating with carbon (coke). -since iron below carbon in the reactivity series.

EXTRACTION OF IRON STEP 1 : CONCENTRATION



The ore is crushed in crushers and is broken to small pieces.



It is concentrated with gravity separation process in which it is washed with water to remove clay, sand, etc.

STEP 2 : CALCINATION



The ore is then heated in absence of air (calcined).

EXTRACTION OF IRON STEP 3 : SMELTING



The concentrated ore is mixed with calculated quantity of coke, limestone and the mixture is put in the blast furnace from top.

Blast Furnace

EXTRACTION OF IRON REACTION IN BLAST FURNACE

1)

Formation of carbon monoxide:



Coke burns in air to form carbon dioxide & a lot of heat is produced (about 1875 K). C + O2 → CO2 + Heat



This CO2 further racts with more coke and is reduced to CO. C + CO2 → 2CO

EXTRACTION OF IRON REACTION IN BLAST FURNACE

2) Reduction of ores to iron:



Iron ores is reduced to Iron by CO.



This molten Iron is collected at the bottom of the furnace. Fe2O3 + 3CO → 2Fe + 3CO2

Heamatite

Fe3O4 + 4CO → 3Fe + 4CO2

Magnetite

EXTRACTION OF IRON FUNCTION OF LIMESTONE



Acts as flux to remove sand from haematite in form of liquid slag.



Limestone decomposes to produce calcium oxide (CaO) and CO2. CaCO3 + heat → CaO + CO2



This CaO reacts with silica (sand) present in the ore to form slag (CaSiO3) CaO + SiO2→ CaSiO3

COMMERCIAL FORM OF IRON 

3 major forms of iron.

1) Cast Iron Contain 2-5% carbon along with traces of other impurities.

2) Wrought iron The purest form of iron and contain carbon to the extent of 0.25%.

3) Steel Contains 0.5 to 1.5% carbon along with variying amount of other elements.

TRY THIS 1)

Name three ores of Iron.

2)

Write the chemical reaction taking place in a blast furnace during extraction of Iron.

3)

What 3 major types of iron. How do they differ from each other?

4)

Draw a neat labeled diagram of Blast Furnace.

REVISION 1)

What distinguishes a transition metal from a representative metal?

2)

Why zinc is not considered as transition metal?

3)

Explain why atomic radii decrease very gradually from Sc to Cu.