Answer:
Mercury is used in thermometers because it has high coefficient of expansion. Hence, the slightest change in temperature is notable when it's used in a thermometer.
Also, mercury has a freezing point of -38.83 °C and boiling point at 356.7 °C, this gives a very big range to measure temperatures for may general purposes, also it does not stick to(wet) the capillary wall of the thermometers, and its easy to obtain in its elemental form.
Step-by-step explanation: