13.1 First Row d-block Elements

Syllabus

What does this mean?

The Periodic Table.

There is nothing “God-given” about the Periodic Table.

We use the current shape because it is convenient.

Sixth form students think of it in blocks, according to the type of orbital in the outer electrons are in (mostly).

We generally put the f-block at the bottom, mostly because it’s out of the way – and many of the elements are so radioactive that they’re essentially useless.

We name the elements either Lanthanides (or Lanthanoids) and Actinides (Actinoids) after the first element in that row of the f-block

To be consistent with what we did with the d-block, we should put the f-block in as below.

But you very rarely see the table in this form

(note H can be placed in more than one spot. Why?)

What is the difference between a Transition Element and a d-block element?

Not much.

Most d-block elements are Transition elements but we exclude Zn and Sc because they don’t have the usual of Transition Element properties.

Properties of Transition Elements.

Fill in the electron box for atoms of the top row d-block elements

Fill in the electron box for common ions of the top row d-block elements

Zn²⁺ is the only ion that Zinc forms.

Sc³⁺ is (almost) the only ion that Scandium forms

We need to exclude these elements from the list of Transition Elements because they have the wrong properties so we say:

“A Transition element is a ____-block element that forms ions with an _____________________ d sub-shell”

Videos

Variable Oxidation States

You don’t have to learn these but…

Notice that on the left (before the half-way point) the most stable Oxidation states are usually the highest available.

But on the right, low oxidation states are most common and that this is +2 – which all Transition elements can do.

High oxidation state Mn/Cr compounds make good oxidising agents because they can fall to a stable low oxidation state

Eg: MnO₄^---> Mn²⁺

Oxidation State = _____ --> Oxidation State = _____

Eg: Cr₂O₇^2---> Cr³⁺

Oxidation State = _____ --> Oxidation State = _____

Successive ionisation energies

1. Why does Aluminium need to lose 3 electrons?

2. Look at the diagram above, why is it unlikely to lose even more electrons?

3. Look at the diagram below. How does it show why Transition elements can form variable oxidation states?

1. Why might there be a smaller difference between successive IEs for d-block elements? (think about which shell the next electron comes from)

Colourful Compounds

Because Zn & Sc are not Transition elements, we expect their compounds to be ______________ when solid & to dissolve to form _______________ solutions.

You don’t need to be able to explain how the colour is formed in detail yet but you should know the basic Physics.

When complex ions form, the d-orbitals are not at the same energy.

Energy is ____________ to promote electrons from lower to higher orbitals

Energy is ________________ to frequency.

So different energy gaps absorb different frequencies

1. If a compound absorbed the blue end of the spectrum what colour would it be?

2. The electronic Configuration of Zn²⁺ is 1s² 2s² 2p⁶ 3s² 3p⁶4s⁰ 3d¹⁰. Why aren’t Zn (II) solutions colourful?

3. The electronic Configuration of Sc³⁺ is 1s² 2s² 2p⁶ 3s² 3p⁶4s⁰ 3d⁰. Why aren’t Sc (III) solutions colourful?

Videos

Transition Metal Complexes.

A Complex consists of:

1. A central metal ion

2. Co-ordinately bonded Ligands

What is a ligand?

A co-ordinate bond is a covalent bond in which _________________________

________________________________________________________________

So, to be a ligand a species needs to possess a _______________________.

It can be a neutral compound (NH₃, H₂O) or an ion (Cl^-, OH^-)

Hexaqua complexes.

Water is a fairly small ligand.

So, 6 water ligands can fit around metal ions.

Since water is neutral, the charge of the complex is the charge of the central ion. In these cases Co²⁺ and Fe²⁺

The co-ordination number of these complexes is 6 (6 coordinate bonds)

Monodentate, bidentate, polydentate ligands.

Water has 2 lone pairs but can only form one coordinate bond to a metal ion since the lone pairs are on the same atom.

Chloride ions have 4 lone pairs but, again, forms only one co-ordinate bond since the lone pairs are on the same atom.

The same is true of Ammonia.

So, Water, Ammonia and Chloride ions are said to be monodentate ligands because _________________________________________________________

Bidentate ligands.

A bidentate ligand should be able to __________________________________

________________________________________________________________

To do this it would need _________ lone pairs, generally on atoms that are separated by 2 Carbon atoms.

The two most common bidentate ligands

This complex contains ______ ligands

Its coordination number is _______

The charge of the central ion must be _____ because

This complex contains ______ ligands Its coordination number is _______

The charge of the central ion must be _____ because

Polydentate ligands.

-can form more than 2 co-ordinate bonds.The most common one is EDTA^4- .

DON'T LEARN ITS STRUCTURE

This molecule should be able to form _______ coordinate bonds.

EDTA is used can be used to remove Lead and other heavy metals from blood.

The Lead ions form a complex which dissolves in urine and is removed from the body.

It can also be used to remove Calcium ions from water.

Hard water (high Ca²⁺) concentration causes which problems?

It can also remove them from the body if they are causing medical problems.
Oily foods go slowly rancid - but they go rancid faster when there are metal ions to catalyse the reaction. So, adding EDTA preserves the food for longer.