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Rubidium (Rb)
Reactivity series
Elements
Reactivity
Potassium Sodium Calcium Magnesium Aluminium Manganese Chromium Zinc
Iron Cadmium Tin
Lead Hydrogen Copper Mercury Silver Gold Platinum
Most reactive
Least reactive
Metals are arranged in the reactivity series.
(See also: Fluorine.)
Reactivity series
The series of metals organised
in order of their reactivity, with the most reactive metals, such as potassium, at the top and the least reactive metals, such as platinum, at the bottom. Hydrogen is usually included in the series for comparative purposes.
Reduce, reduction
To remove oxygen from or add hydrogen to a compound.
Relative atomic mass
In the past, a measure of the mass of an atom on a scale relative to the mass of an atom of hydrogen, where hydrogen has an atomic mass of 1.
Nowadays, a measure of the mass of an atom is made relative to the mass of one-twelfth of an atom of carbon-12. If the relative atomic mass is given as a rounded figure, it is called an approximate relative atomic mass. For example, the approximate relative atomic mass of chlorine is 35, calcium 40 and gold 197.
Rhenium (Re)
Element 75 on the periodic table. A very dense element and one of the transition metals.
It was discovered in 1925 by the German chemists Ida and Walter Noddack and Otto Carl Berg. It has few direct uses.
Rhodium (Rh)
Element 45 on the periodic table. A rare, silver-white member of the transition metals.
Rhodium is normally obtained as a by-product from the refining of copper and nickel. It is a precious
 Reactivity series – Because metals differ in their reactivity, if a more reactive metal is placed in a solution of a less reactive metal compound, a reaction occurs that takes the reactive metal into solution and forces the less reactive metal out of solution, forming a precipitate. This important reaction is used in refining some metals.
 Reactivity series – Copper is more reactive than silver. A copper strip placed in a silver nitrate solution causes the silver to be precipitated onto the copper strip.
metal and will not tarnish. It is often electroplated as a coating onto other metals to make a shiny, non-tarnishing finish on tableware and jewellery. Its other main use is as an alloying metal to make platinum harder.
Rubidium (Rb)
Element 37 on the periodic table. A member of group 1 (the alkali metals). This silvery metal is
the second most reactive metal. Rubidium reacts spontaneously in air and water. When it reacts with water, it releases hydrogen gas, which then catches fire.
It was discovered in 1861 by Robert Bunsen and Gustav Kirchhoff. It is named after the red colour that can been seen in a spectrometer. It has to be kept in dry mineral oil or in a hydrogen atmosphere.
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