Reactivity series and ordering metals
Chemical changes • Reactivity of metals
Flashcards
Test your knowledge with interactive flashcards
Key concepts
What you'll likely be quizzed about
Definition of reactivity for metals
Reactivity of a metal describes how readily the metal atom loses electrons to form a positive ion (cation). Cause: metal atoms lose outer electrons. Effect: formation of M+ or M2+ ions leads to chemical change and energy release. Limiting factors include experimental conditions such as temperature, concentration, surface area and the presence of oxide layers. Experimental context determines the observed speed and vigour of reactions and can change apparent reactivity.
Reaction with water and dilute acids
Cause: a metal that loses electrons easily reduces H+ ions from acids or water to hydrogen gas, or reacts with water to form hydroxides and hydrogen. Effect: visible signs include bubbling of hydrogen gas, heat release and dissolving of the metal into solution as ions. Observations: very reactive metals (e.g., potassium, sodium) react vigorously and may ignite; less reactive metals produce slow bubbling or only react with steam or hot water; unreactive metals (e.g., copper) show no reaction with dilute acids or cold water under standard conditions.
Displacement reactions as a test
Cause: a more reactive metal has a stronger tendency to form positive ions than a less reactive metal ion in solution. Effect: a metal higher in the series displaces ions of a metal lower in the series from solution (e.g., zinc metal displaces copper ions). Experimental procedure: place a strip of one metal into a solution containing ions of another metal. A change such as deposition of a solid metal, colour change, or loss of metal from solution indicates displacement and therefore relative reactivity.
Deduction of order from experimental results
Cause: comparison of reaction vigour with water, reaction with dilute acids, and results of displacement reactions yields relative tendencies to form positive ions. Effect: ranking metals by observed reactivity produces the reactivity series. Practical approach: record which metals react with cold water, which react only with steam or hot water, which react with dilute acid to produce hydrogen, and which displace which ions in solution. Combine results to deduce an order consistent across tests.
Standard order for the given metals
The accepted order from most reactive to least reactive for the specified metals is: potassium, sodium, lithium, calcium, magnesium, zinc, iron, copper. Cause: potassium and sodium lose electrons most readily among the list, producing vigorous reactions; copper shows negligible reaction with dilute acids because it does not form H+ reduction under these conditions. Effect: the order predicts outcomes of water, acid and displacement tests.
Key notes
Important points to keep in mind