MCQ Detailed View

Tin (Sn) is a chemical element that exists in different allotropic forms depending on temperature. The two important allotropes are grey tin (α-tin) and white tin (β-tin). Grey tin has a diamond-cubic crystal structure and behaves more like a non-metal, while white tin has a tetragonal structure and is metallic in nature. The conversion between these two forms occurs at a specific temperature known as the transition temperature.

The transition temperature for tin is 18 °C. Below this temperature, white tin tends to convert into grey tin. This change is slow at room temperature but becomes significant in colder conditions. Above 18 °C, grey tin is unstable and gradually transforms back into white tin, which is the metallic form commonly used in industrial and domestic applications.

The phenomenon of transformation between grey tin and white tin is sometimes called “tin pest” or “tin disease”. This is because the formation of grey tin makes the material brittle and powdery, leading to deterioration of objects made from tin in cold climates. This property has been studied historically, as tin-based materials in colder regions would often degrade due to this allotrope conversion.

In terms of structure, grey tin is less dense and appears as a dull powder, while white tin is shiny, ductile, and metallic. The stability of white tin above 18 °C explains why it is the more commonly found allotrope in everyday use. Understanding this transition is important in inorganic chemistry and in the study of phase changes of elements.

Thus, the transition temperature between grey tin and white tin is 18 °C, making option B correct.