Final answer:
The unit of measurement for atmospheric pressure is the Pascal (Pa) or atmosphere (atm). A barometer, like a mercury barometer, is used to measure atmospheric pressure.
Step-by-step explanation:
The proper SI unit for atmospheric pressure is the Pascal (Pa). Atmospheric pressure can also be measured using the unit atmosphere (atm). In chemistry, pressure is commonly measured in terms of atmospheres where 1 atm is atmospheric pressure at sea level. A barometer is often used to measure atmospheric pressure, such as a mercury barometer which determines pressure based on the height of the mercury column.