Tin is unaffected by air at ordinary temperature due to its?

1. Analyze the question

The question asks why Tin (Sn) remains stable and does not react with air (oxygen) at ordinary room temperatures, despite being a metal.

2. Explain the concept

In chemistry, the reactivity of a metal is often linked to its electropositive character (its tendency to lose electrons to form positive ions).

• Electropositive character: Highly electropositive metals (like Sodium or Potassium) react vigorously with air and water because they lose electrons very easily.
• Passivation: Some metals, like Tin and Aluminum, form a very thin, invisible, and non-porous layer of oxide on their surface when exposed to air. This layer acts as a protective "shield" that prevents further reaction with oxygen or moisture.
• Tin's Position: Tin is located in the middle of the reactivity series. It is not as reactive as the alkali metals. Because it has a relatively weak electropositive character compared to highly reactive metals, it does not readily lose electrons to oxygen at room temperature, and the protective oxide film keeps it stable.

3. Show the solution

• Option A (Low melting point): Tin has a relatively low melting point (231.9°C), but this property relates to its physical state when heated, not its chemical resistance to air at room temperature.
• Option B (Weak electropositive character): Because Tin is not strongly electropositive, it does not have a high affinity for oxygen at room temperature. Combined with the formation of a protective oxide layer, this makes it resistant to atmospheric corrosion.
• Option C (High boiling point): This is a physical property and does not explain chemical reactivity with air.
• Option D (White lustrous appearance): This describes the physical look of the metal (its luster), which is a result of its metallic bonding, but it is not the reason for its chemical stability.

4. Identify the answer

The correct option is B. The weak electropositive character of Tin means it does not readily react with oxygen under ordinary conditions.

5. Exam Tip

When dealing with "reactivity" questions in JAMB, always look for keywords like "electropositive," "electronegative," or "oxide layer." If a metal is described as "unaffected by air," it is almost always due to the formation of a protective oxide film or a low tendency to lose electrons (weak electropositive character).