Extracting Metals towards the Top of the Activity Series: A Detailed Summary

Activity series of elements at the top of the series include potassium (K), sodium (Na), calcium (Ca), Magnesium (Mg) and others. Metals at the peak of the reactivity range cannot be produced from their compounds via carbon (C) reduction. This happens because metals have a higher affinity for oxygen (O₂) over carbon (C), making them more reactive.

Metals near the peak of the reactivity range are thus obtained through the electrolysis of corresponding molten chlorides (Cl^-). When an electric current is conducted over molten sodium (Na) metal, positive ions are created at the cathode (oxidising or positive electrode). Consequently, chloride ions, which are negative ions, were deposited in the type of chlorine at the anode (reducing or negative electrode). This method is known as electrolytic reduction. Metals extracted through electrolytic reduction are pure.

In this article, let’s understand more about activity series and extracting metals towards the top of the activity series using certain examples and its reaction.

What is an Activity Series?

The periodic table's reactivity is determined by the reactivity series, often referred to as the activity series. This series is structured to ensure that the highly reactive metal falls prior and on top of the least reactive metal.

The activity series of metals listed in decreasing sequence of activity. Upon displacement studies, the accompanying series, referred to as the activity or reactivity series was generated.

Extraction of Sodium (Na) Metal from Sodium Chloride (NaCl)

Molten sodium chloride (NaCl) releases sodium (Na⁺) metal at the cathode and chlorine (Cl^-) at the anode when an electric current is applied to it.

\[N{a^ + } + {e^ - } \to Na\]

\[2C{l^ - } \to C{l_2}\left( g \right) + 2{e^ - }\]

\[2NaCl\left( {molten} \right) \to 2Na\left( s \right) + C{l_2}\left( g \right)\]

The only way to get sodium (Na) metal is by melting sodium chloride (NaCl), not by dissolving it in water. This is because sodium (Na) metal accumulated at the cathode combines with water contained in the solution to generate sodium hydroxide (NaOH) when an electric current is transmitted through an aqueous solution of sodium chloride (NaCl).

\[4Na + 2{H_2}O \to 4NaOH\]

Extraction of Aluminum (Al) Metal from Aluminium Oxide (Al₂O₃)

In a manner similar to how sodium (Na) metal is removed, aluminium metal is reduced electrolytically. The positively charged aluminium (Al) ion is drawn to the cathode when an electric current is run through the molten aluminium oxide. Aluminum (Al) metal is created at the cathode when the aluminium (Al) ion receives electrons from the cathode.

However, because they had a negative charge, oxide ions were attracted to the anode. Oxide ions lose their electrons at the anode, forming oxygen gas.

\[A{l^{ + + + }} + 3{e^ - } \to Al\]

\[2{O^{ - - }} \to {O_2}\left( g \right) + 4{e^ - }\]

\[2A{l_2}{O_3} \to 4Al\left( s \right) + {O_2}\left( g \right)\]

Metal Refining

With the exception of those acquired through electrolytic reduction, metals obtained through various extraction procedures all contain a variety of contaminants. In order to produce pure metals, impure metals acquired through various processes are refined.

Interesting Facts

• The most reactive activity series of metals potentially react in the presence of air or moisture. These metals include calcium, sodium, and potassium.

• Copper and silver, the metals at the bottom of the activity series, can also be found together in their sulphide or oxide ores.

• The oxides, sulphides, and carbonates that make up the majority of the earth's crust are composed of the metals in the middle of the activity series.

• Impure metals can be refined using a variety of techniques, however electrolytic refining is among the quite used ones.

• Several metals are refined electrically, including copper, zinc, silver, gold, etc.

Key Features to Remember

• Metals towards the top of the activity (or) reactivity series have a high level of reactivity. By heating with carbon, they cannot be extracted from their compounds.

• Carbon, for instance, is unable to convert the oxides of sodium (Na), magnesium (Mg), calcium (Ca), aluminium (Al), etc. into the corresponding metals. This is due to the fact that certain metals are more apt to bind oxygen than carbon.

• Extracting metals towards the top of the activity series can be obtained mainly through electrolytic reduction.

• Most of the time metals extracted through electrolytic reduction will be in pure form.