Explaining the trend in the reactivity of the halogens
4 marks · NormalThe table shows some properties of Group 7 elements.
| Element | Colour at room temperature | State at room temperature | Melting point (°C) |
|---|---|---|---|
| Chlorine | Green | Gas | -101 |
| Bromine | Red-brown | Liquid | -7 |
| Iodine | Dark grey | Solid | 114 |
Predict the appearance and physical state of astatine at room temperature.
Suggest a melting point for astatine, based on the trend in the table.
Work this out on paper, then compare with the answer and worked solution below. With a free account you can submit written answers for marking.
Show answer
(a) Very dark grey or black solid · must show Very dark grey or black, Solid
(b) Above 114°C, likely 180–220°C
Common mistakes: Predicting liquid or gas state; Unrealistic melting point
Show mark scheme and worked solution
Marking points
B1 (a) · 1 mark · Predicts very dark grey or black for colour
B2 (a) · 1 mark · Predicts solid state
M1 (b) · 1 mark · Recognises melting point increases down the group
A1 (b) · 1 mark · Suggests melting point above 114 °C, accepts range 180–220°C
Worked solution
a) The appearance will be very dark grey or black, and it will be a solid at room temperature. b) The melting point should be higher than iodine, so above 114 °C. Based on the trend, a reasonable estimate is about 200 °C.