Question

The following table shows some information about the elements of the 7A group of the Modern Periodic Table.

Name	State at room temperature	Colour
Chlorine	Gas	Yellow- green
Bromine	Liquid	Brown
Iodine	?	?
Astatine	Solid	Black

Which of the following information completes the given table?
(A) State – liquid; Colour – Black
(B) State – liquid; Colour – Green
(C) State – solid; Colour – Grey
(D) State – solid; Colour – Yellow

Answer 1

Hint: The halogens darken in colour as the group is descended, with fluorine being a very pale-yellow gas, chlorine being a greenish-yellow liquid and bromine also being a volatile liquid of a reddish-brown colour.

Complete step by step solution:
To solve this question, we need to be familiar with the physical properties of Iodine, so let us analyse Iodine as an element to help us answer this question.
- Iodine is a chemical element with atomic number of 53. The symbol of this element is I.
- It is the heaviest of the halogens which is stable, it exists as a purple or gray colored non-metallic solid at standard conditions. This form melts to form a deep violet liquid at ${{114}^{\circ }}C$ .
- Iodine boils to a violet gas at ${{184}^{\circ }}C$ .
- However, it sublimes easily with gentle heat, resulting in a widespread misconception that it does not melt. This is because Iodine conforms to the prevailing trend of the colour of halogens darkening from top to bottom of the group as it exists as a shiny black crystalline solid that has a melting point of 114 °C and boiling point of 183 °C.
- This trend is supposed to occur because the wavelengths of visible light absorbed by the halogens increase down the group.
So, we can conclude that Iodine is solid at room temperature and grey in color.
Therefore correct answer is (C) State – solid; Colour – Grey

Note:
Remember that Iodine vapours are violet in colour but solid iodine is grey in colour at room temperature. Keep in mind that Bromine and Chlorine are gases at room temperature but Iodine behaves as a solid at room temperature.