what does atm mean in chemistry

Atm in chemistry stands for **atmosphere**, which is a non-SI unit of pressure. It represents the standard atmospheric pressure at mean sea level. One atmosphere (1 atm) is precisely defined as 101,325 Pascals (Pa). This unit is fundamental in understanding the behavior of gases, particularly when applying gas laws like the Ideal Gas Law. Although the SI unit is the Pascal, 'atm' is still widely used in chemical and physical calculations to provide a familiar reference point for gas behavior.