Core Concepts
In this article, you will learn about the Reactivity Series, including its significance and its applications. After reading this article, you will be able to understand the nature of the Reactivity Series as well as its uses and functions.
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Defining the Reactivity Series
The reactivity series is a hierarchical arrangement of elements based on their relative tendency to undergo chemical reactions. It provides a systematic framework for comparing and ranking elements according to their reactivity. The series allows scientists to predict the behavior of elements when they come into contact with other substances and provides insights into the types of chemical reactions they are likely to undergo. Elements at the top of the reactivity series are the most reactive, while those at the bottom are the least reactive. This concept is essential in understanding various chemical phenomena, such as the extraction of metals, predicting reaction outcomes, and preventing corrosion.
Ordering the Reactivity Series
The reactivity series follows a general order, although slight variations can occur based on specific reaction conditions. Here is a commonly accepted order of elements in the reactivity series:
It is important to note that this list provides a general guideline and may vary slightly depending on the specific reaction being considered.
Understanding Reactivity Trends
Alkali Metals and Alkaline Earth Metals
Alkali metals such as potassium, sodium, and calcium are all highly reactive elements. Because of their low ionization energies, they easily shed their outermost electrons, generating positive ions. The diminishing strength of the metallic link retaining the outermost electron enhances reactivity as we proceed down the group.
Transition Metals
Transition metals with moderate reactivity include iron and zinc. They may form compounds with a wide spectrum of elements and have numerous oxidation states. Because of their capacity to assist chemical processes without being consumed in the process, transition metals are frequently utilized as catalysts.
Noble Metals
Noble metals such as gold and platinum are distinguished by their low reactivity. They have stable electron configurations with entire or almost full outer electron shells, which makes them less reactive than other compounds. Because of their stability, noble metals may resist corrosion and stay in their pristine state in nature.
Significance of the Reactivity Series
Predicting and Balancing Reactions
The reactivity series can be used to forecast the results of chemical processes. Highly reactive components are more likely to react with other substances, whereas less reactive elements are less likely to react. Furthermore, by distinguishing the elements undergoing oxidation and reduction, the reactivity series aids in balancing redox equations.
Metallurgy and Extraction of Metals
The reactivity series is important in metallurgy, which is the science of recovering metals from their ores. Electrolysis is used to obtain highly reactive metals such as potassium and sodium. Copper and silver, on the other hand, may be extracted using less reactive procedures such as smelting and reduction.
Corrosion Prevention
Understanding the reactivity series is critical in the fight against corrosion. Knowing the relative reactivity of metals allows for the implementation of suitable protective measures. Sacrificial anodes comprised of highly reactive metals such as zinc, for example, are used to preserve iron or steel buildings against corrosion.
Practical Applications of the Reactivity Series
The reaction of Metals and Hydrogen with Water or Steam
| Element | Reaction with Water/Steam |
| potassium | Reacts very violently to cold water |
| sodium | Reacts violently to cold water |
| calcium | – |
| magnesium | Reacts very slowly with water, but rapidly with steam |
| zinc | Only reacts when powdered and heated strongly in steam |
| iron | Does not react with water, but reacts slowly with steam |
| hydrogen | No reaction |
| copper | No reaction with water or steam |
Reaction with cold water
- The more reactive metals will react with cold water to form metal hydroxide and hydrogen gas.
- Potassium, sodium, and calcium all undergo reactions with cold water as they are the most reactive metals.
For Example,
Reaction with steam
Metals just below calcium in the reactivity series do not react with cold water but will react with steam to form a metal oxide and hydrogen gas.
For example,
The reaction of metals and hydrogen with dilute (HCl) Acid
| Element | Reaction with dilute hydrochloric acid |
| potassium | Very violent – very explosive |
| sodium | Very violent – explosive |
| calcium | Very rapid – lots of hydrogen gas produced |
| magnesium | Rapid – bubbles of hydrogen produced steadily |
| zinc | Slow – bubbles of hydrogen produced slowly |
| iron | Slow reaction – some bubbles produced |
| hydrogen | No reaction |
| copper | No reaction |
Reaction with Dilute Acid
- Only metals above hydrogen in the reactivity series will react with dilute acids
- Unreactive metals below hydrogen, such as gold, silver, and copper, do not react with acids
- The more reactive the metal then the more vigorous the reaction will be
- Metals that are placed high on the reactivity series such as potassium and sodium are very dangerous and react explosively with acids
- When acids react with metals, they form a salt and hydrogen gas
The general equation is:
Metal + Acid → Salt + Hydrogen
Reaction with Oxygen
- Some reactive metals, such as the alkali metals, react easily with oxygen
- Silver, copper, and iron can also react with oxygen although much more slowly
- When metals react with oxygen, a metal oxide is formed.
For example,
Metal + Oxygen → Metal Oxide
- Oxygen has no effect on gold.
The reactivity series is a key concept in chemistry that explains elemental behavior and its role in chemical processes. It is a useful instrument in the area of chemical research, whether it’s anticipating reaction outcomes, understanding metal extraction methods, or implementing corrosion prevention measures.
Why does Iron corrode in the presence of Copper but not in the presence of Zinc?
Answer – Ongoing from the bottom to the top of the series, the tendency to lose electrons increases, and hence, the oxidizing nature of metals increases.
Copper lies below Iron in the reactivity series, hence, Iron is a more oxidizable/ reactive metal than copper. Hence, iron corrodes in the presence of copper. While Zinc lies above Iron in the reactivity series and is more reactive than iron. Thus, in the presence of Zinc, iron does not corrode.
What happens when you place a Copper strip in a jar containing the MgSO4 solution?
Answer – Since Copper lies below magnesium in the reactivity series, it cannot replace magnesium from its salt solution. Hence, no change is observed when a Cu strip is placed in the MgSO4 solution.
Further Reading
More about metals
Interactive Periodic Table
More about Periodic Trends