Transition metals - AQATypical transition elements
The transition elements are metals. They have high melting points and densities, and are strong and hard. They form coloured compounds and act as catalysts.
The elements below have properties that are typical of transition elements:
chromium, Cr
manganese, Mn
iron, Fe
cobalt, Co
nickel, Ni
copper, Cu
The table shows the melting point and density of some transition elements, compared to three metals in the periodic tableA tabular representation of all known elements in order based on atomic number, eg all the noble gases are found on the right of the periodic table. that are not transition elements.
Metal
Position
Melting point
Density
Sodium
Group 1
98°C
0.97 g/cm3
Magnesium
Group 2
650°C
1.74 g/cm3
Aluminium
Group 3
660°C
2.70 g/cm3
Chromium
Transition elements
1890°C
7.19 g/cm3
Manganese
Transition elements
1240°C
7.20 g/cm3
Iron
Transition elements
1538°C
7.87 g/cm3
Cobalt
Transition elements
1492°C
8.90 g/cm3
Nickel
Transition elements
1453°C
8.90 g/cm3
Copper
Transition elements
1083°C
8.92 g/cm3
Metal
Sodium
Position
Group 1
Melting point
98°C
Density
0.97 g/cm3
Metal
Magnesium
Position
Group 2
Melting point
650°C
Density
1.74 g/cm3
Metal
Aluminium
Position
Group 3
Melting point
660°C
Density
2.70 g/cm3
Metal
Chromium
Position
Transition elements
Melting point
1890°C
Density
7.19 g/cm3
Metal
Manganese
Position
Transition elements
Melting point
1240°C
Density
7.20 g/cm3
Metal
Iron
Position
Transition elements
Melting point
1538°C
Density
7.87 g/cm3
Metal
Cobalt
Position
Transition elements
Melting point
1492°C
Density
8.90 g/cm3
Metal
Nickel
Position
Transition elements
Melting point
1453°C
Density
8.90 g/cm3
Metal
Copper
Position
Transition elements
Melting point
1083°C
Density
8.92 g/cm3
Worked example
Compare the properties of sodium and chromium. How does the data show that chromium is a typical transition element, and sodium is a typical group 1 metal?
Chromium has a much higher melting pointThe temperature at which a solid changes into a liquid as it is heated. than sodium. The densityA measure of compactness and the ratio of mass to volume. It is usually measured in kilograms per metre cubed (kg/m3) or grams per centimetre cubed (g/cm3). of chromium is also greater than sodium. Most transition elements have high melting points and densities, so chromium is a typical transition element. The group 1 elements have low melting points and densities, so sodium is a typical group 1 element.
Question
Predict the differences in the hardness and strength of nickel and potassium. Give a reason for your prediction.
Nickel is harder and stronger than potassium. The reason for this prediction is that nickel is a transition element and potassium is in group 1.
