Which of the following is the correct arrangement of the given metals in descending order of their reactivity?
Zinc, Iron, Magnesium, Sodium

Question

Accepted Answer

The correct arrangement of the given metals in descending order of their reactivity is Sodium > Magnesium > Zinc > Iron, as stated in Option 4. Here's a detailed explanation supporting this arrangement:

1. **Sodium**: Sodium is an alkali metal and is highly reactive. It reacts vigorously with water and oxygen, which places it at the top of the reactivity series among the given metals. Its high reactivity is due to its tendency to lose its single valence electron easily, forming a positive ion.

2. **Magnesium**: Magnesium is an alkaline earth metal and is less reactive than sodium but more reactive than zinc and iron. It reacts with water at higher temperatures and with acids to produce hydrogen gas. Magnesium's reactivity is due to its ability to lose two electrons to form a stable ionic compound.

3. **Zinc**: Zinc is less reactive than magnesium. It reacts with acids and can displace less reactive metals from their compounds. However, it does not react as vigorously with water as sodium or magnesium.

4. **Iron**: Iron is the least reactive among the given metals. It reacts slowly with water and oxygen, forming rust over time. Iron's reactivity is lower than that of zinc, magnesium, and sodium, which places it at the bottom of this list.

**Explanation of Incorrect Options:**

- **Option 1 (Zinc > Iron > Magnesium > Sodium)**: This option incorrectly places zinc as more reactive than magnesium and sodium, which is not true. Sodium and magnesium are both more reactive than zinc.

- **Option 2 (Sodium > Magnesium > Iron > Zinc)**: While this option correctly places sodium and magnesium at the top, it incorrectly suggests that iron is more reactive than zinc, which is not the case.

- **Option 3 (Sodium > Zinc > Magnesium > Iron)**: This option incorrectly places zinc as more reactive than magnesium. Magnesium is more reactive than zinc, as it can displace zinc from its compounds.

In conclusion, Option 4 is correct because it accurately reflects the reactivity series of the given metals, with sodium being the most reactive and iron the least reactive.