The Transition Elements
In the centre of the Periodic Table there is a large block of metallic elements. We call these the transition metals or transition elements.
Many of the transition elements have similar properties, but they are also different from the other elements in the Periodic Table.
The Transition metals have a typical metallic structure which explains most of their properties The metal's atoms exist in a giant structure held together by metallic bonds, and the outer electrons of each atom can move about freely within the metal.
Like all metals, transition metals are very good conductors of electricity and heat because delocalised electrons carry the electrical current or the heat energy through the metal. The transition metals are also hard, tough and strong, yet we can bend or hammer them into useful shapes.
With the exception of mecury, which is liquid at room temperature, the Transition metals have very high melting points.
Many properties of the Transition elements are due to the arrangement of electrons in their atoms. In these elements as lower energy level is filled up between Groups 2 and 3. This partly-filled lower energy level explains why transition metals form brightly coloured compounds. It also results in their use as catalysts.
The Transition Elements 2
The Transition elements are much less reactive than the metals in Group 1. This means they do not react as easily with oxygen or water as the alkali metals. In other words, they corrode very slowly. Together with their physical properties, this makes the Transition elements very useful as structural materials.
They are particularly useful when they are mixed together with each other, or with other elements to make alloys. Iron mixed Carbon in Steels is the best known of these.
Other very useful alloys of transition elements are:
- brass - a combination of Zinc and Copper
- cupro-nickel - a very hard alloy of copper and nickel, used to make the coins we use in our currency.
The Transition Elements 3
Many of the transition metals form coloured compounds. These include some very common compounds that we use in the laboratory. For example, Potassium Dichromate is orange- the orange colour is due to the Chromium ion in the compound. Similarly Copper Sulfate is blue (from the Copper ion) and Potassium Manganate is purple (from the Manganese ion).
The colours which are produced by the transition elements are important in the world around us. For example, the colours of many minerals, rocks and gem stones are the result of transition element ions.
A reddish-brown colour in a rock is often the result of Iron ores. The blue colour of Sapphires and the green of Emeralds are both due to transition element ions in the structure of the crystal.
We use the coloured ions of transition elements in many different ways. Lots of pottery glazes contain transition metal ions to give bright colours. As copper weathers it produces a green film of basic copper carbonate. This green patina is very attractive and is generally called 'verdigris'. It is one reason why copper is used for many statues.