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GCSE Chemistry Revision
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GCSE Chemistry revision
Comparison with Group 1 elements
Properties of transition metals (chemistry only)
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Key knowledge
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Introduction
- Unlike typical metals, alkali metals are relatively soft, have low densities, and have low melting points.
- Alkali metals are far more reactive than most other metals, reacting vigorously with water, oxygen, and Group 7 elements such as chlorine.
Trends Down Group 1
- As you go down Group 1, the reactivity of the alkali metals increases, with caesium being so reactive it can ignite spontaneously at room temperature.
- As you go down Group 1, the melting points and boiling points of the alkali metals decrease.
Why Does Reactivity Increase Down the Group?
- As you go down Group 1, the atomic radius increases, so the outermost electron is further from the positive nucleus.
- The greater distance between the nucleus and the outer electron weakens the electrostatic attractive force, making the electron easier to lose and the atom more reactive.
Formation of Coloured Compounds
- Transition elements characteristically form brightly coloured compounds (such as blue copper compounds or green iron compounds), whereas Group I compounds are white.
High Density and Melting Points of Transition Elements
- Transition elements are tough, structural metals characterised by high densities and high melting points compared to Group 1 metals.
Comparison of Transition Metals and Group 1 Elements
- Physical Property Differences - Transition metals exhibit higher melting points, higher densities, greater overall strength, and significantly higher hardness than the soft Group 1 alkali metals.
- Chemical Reactivity - Transition metals are much less reactive than Group 1 metals when reacting with oxygen, water, and halogens, reacting far more slowly or requiring much stronger conditions.
- Representative Transition Elements - These general physical and chemical trends are illustrated using key transition elements, specifically chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), and copper (Cu).