Understanding Metal Reactivity Series

The reactivity series is a series of metals arranged in order of their decreasing reactivity. A more reactive metal can displace a less reactive metal from its salt solution. Metals higher in the series are more reactive, meaning they lose electrons more easily than metals lower in the series.

The general order of reactivity from most reactive to least reactive is:

• Potassium (K)
• Sodium (Na)
• Calcium (Ca)
• Magnesium (Mg)
• Aluminium (Al)
• Zinc (Zn)
• Iron (Fe)
• Lead (Pb)
• Hydrogen (H) - included for reference
• Copper (Cu)
• Silver (Ag)
• Gold (Au)
• Platinum (Pt)

We are asked to arrange the metals Sodium, Iron, Copper, and Silver in the decreasing order of their reactivity.

Let's locate these metals in the reactivity series:

• Sodium (Na) is high in the series.
• Iron (Fe) is below Aluminium and Zinc.
• Copper (Cu) is below Iron.
• Silver (Ag) is below Copper, towards the very bottom.

Arranging these four metals from most reactive (highest in the series) to least reactive (lowest in the series), we get the following order:

Sodium > Iron > Copper > Silver

This can be represented using chemical symbols and the greater than sign:

$\text{Na} > \text{Fe} > \text{Cu} > \text{Ag}$

Now, let's examine the given options to find the one that matches this decreasing order of reactivity.

• Option 1: Iron, Sodium, Silver, Copper - Incorrect (Sodium is more reactive than Iron)
• Option 2: Silver, Copper, Iron, Sodium - Incorrect (This is increasing order, and the relative positions are wrong)
• Option 3: Sodium, Copper, Silver, Iron - Incorrect (Iron is more reactive than Copper and Silver)
• Option 4: Sodium, Iron, Copper, Silver - Correct (Matches the order derived from the reactivity series)

Therefore, the correct arrangement of the given metals in the decreasing order of their reactivity is Sodium, Iron, Copper, Silver.

Revision Table: Metal Reactivity Comparison

Additional Information on Metal Reactivity

The reactivity of a metal is related to its tendency to lose electrons and form positive ions. Metals higher in the reactivity series lose electrons more easily than those lower down. This property determines how readily a metal reacts with water, acids, oxygen, and other substances.

• Highly reactive metals like Sodium react vigorously with cold water.
• Moderately reactive metals like Iron react with steam or acids.
• Less reactive metals like Copper and Silver do not react with water or dilute acids. Copper reacts with oxygen upon heating, while Silver is even less reactive.

Displacement reactions are a key concept demonstrating the reactivity series. For example, if an iron nail is placed in a copper sulfate solution, the more reactive iron displaces copper, leading to the deposition of copper on the iron nail and the formation of iron sulfate.

$\text{Fe(s)} + \text{CuSO}_4\text{(aq)} \rightarrow \text{FeSO}_4\text{(aq)} + \text{Cu(s)}$

Conversely, if a copper wire is placed in an iron sulfate solution, no reaction occurs because copper is less reactive than iron and cannot displace iron ions from the solution.