9.09.4 Transition Metals

Syllabus

The transition elements are metals with similar properties which are different from those of the elements in Group 1.
Many transition elements have ions with different charges, form coloured compounds and are useful as catalysts.

Students should be able to:

describe the difference compared with Group 1 in melting points, densities, strength, hardness and reactivity with Oxygen, water and Halogens.
exemplify these general properties by reference to Cr, Mn, Fe, Co, Ni, Cu.

What does this mean?

Physical Properties of Metals

In year 7 and 8 we learned that the properties of metals are that they are:

Strong

Hard

Ductile

Dense

Malleable

Good conductors of heat and electricity

Sonorous

High melting and boiling point

Lustrous (shiny)

But we have studied Group 1 metals and these are soft, rather than hard, they float on water, they have low melting and boiling points and they don't stay shiny for long.

So the properties above only really apply in general.

But they apply to Transition Metals much more.

And this group of elements contains the metals which we usually talk about in these terms.

eg Iron, Copper, Zinc, Gold, Silver etc.

What are Transition Elements?

The usual form of the Periodic Table looks like the one to the left.

In Britain we usually label Groups 1-7 and Group 0.

We don't usually give the "pink block" Group numbers because they're all very similar.

We just call them Transition Elements.

Americans sometimes label things from Group 1 to 18 - but then they also drive on the wrong side of the road and can't pronounce Tomato.

How are Transition Metals different to Alkali Metals?

We know that Group 1 elements always form ions with a 1+ charge.

And that Group 2 elements always form ions with a 2+ charge.

This doesn't apply in the Transition block where elements can often have several different charges depending on what reactions they have been involved in.

Copper generally forms Cu2+ but can form Cu+.

So, to avoid confusion we'd refer to their oxides as Copper (II) Oxide and Copper (I) Oxide.

Iron generally forms Fe2+ but can form Fe3+.

So, to avoid confusion we'd refer to their oxides as Iron (II) Oxide and Iron (III) Oxide.

Physically, the metals share some but not all properties. Chemically they're quite different.

Alkali metals react vigorously with Oxygen

eg.

Potassium + Oxygen --> Potassium Oxide

4 K + O2 --> 4 K2O

The Potassium reacts so quickly it catches fire.

Transition elements also usually react with Oxygen, but generally very slowly.

Rusting of Iron is an example, Silver and Copper take years to turn black

Alkali metals react vigorously with Halogens

eg.

Potassium + Chlorine --> Potassium Chloride

2 K + Cl2 --> 2 KCl

Again - this is a very fast reaction that involves flame.

Tranistion elements also often react with halogens.

But Halogens are so reactive that, in this case, there may be a flame too.

Iron + Chlorine --> Iron (III) Chloride

2Fe + 3Cl2 --> 2FeCl3

Typical Properties of Transition Elements

Apart from the usual Physical Properties of metals Transition Elements have some typical properties that Main Block metals do not.

Typically, Copper (II) compounds are Blue, Iron (II) compounds are Green and Iron (III) are Brown/Orange

The coloured compounds of Transition Elements are in contrast to the white compounds of Group1 and 2 elements which dissolve to make colourless solutions - see Sodium Sulfate solution above.