What does pm mean when measuring molecular diameter?

[ZedCar]

Homework Statement

I'm reading a worked problem in my "Fundamentals-of-Physics" textbook, and it states

What is the mean free path l for oxygen molecules at temperature T
= 300 K and pressure p
= 1.0 atm? Assume that the molecular diameter is d
= 290 pm and the gas is ideal.

Homework Equations

The Attempt at a Solution

I was wondering what are the molecular diameter units which I have emboldened? What does pm stand for?

Thank you

 

[gneill]

p is the prefix for pico.

 

[ZedCar]

Okay, thank you!