What is the formula of copper(I) oxide?
- The Roman numeral I shows that the copper ion is Cu+.
- The oxide ion is O2−.
- The charges must add up to zero: two Cu+ ions (2+) balance one O2− ion (2−).
Answer: Cu2O
Properties of transition metals
Chemistry · Atomic structure and the periodic table. The idea in plain words, the rules to remember, the mistake to avoid and a worked example, written and checked by Mega Lecture.
The idea
The transition metals are the block of metals in the middle of the periodic table, between Group 2 and Group 3. Examples are chromium, manganese, iron, cobalt, nickel and copper.
Compared with Group 1 metals they have higher melting points and higher densities, and they are harder and stronger. They are also much less reactive: they react slowly, or not at all, with water, oxygen and the halogens.
They have three special properties. They form ions with different charges, such as Fe2+ and Fe3+. Many of their compounds are coloured. The metals and their compounds are often used as catalysts.
Rules to remember
- Transition metals: high melting point, high density, hard and strong. Group 1 metals: low melting point, low density, soft.
- Group 1 metals react vigorously with cold water; transition metals react slowly or not at all.
- The Roman numeral in a name gives the charge on the metal ion: iron(III) is Fe3+, copper(II) is Cu2+.
- Transition metal compounds are often coloured, e.g. many copper(II) compounds are blue. Group 1 compounds are white.
- Iron is the catalyst in the Haber process; manganese(IV) oxide is a catalyst for the decomposition of hydrogen peroxide.
- A catalyst makes a reaction faster and is not used up, so its mass is the same at the end.
Common mistake
Students choose a property that all metals share, such as conducting electricity or forming positive ions. When asked what is special about transition metals, choose from: ions with different charges, coloured compounds, catalysts.
Worked example
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