How does solar electric propulsion (ion propulsion) work?

How can something as small as an atom move a space craft?

Anything with a propulsion system works when something (usually a gas--sometimes a liquid) pushes out of it. This makes thrust. Any gas or liquid is made of atoms, so jet engines, the space shuttle, and Fourth of July fireworks are all pushed forward by atoms shooting out of them.

Everything from fireworks to space shuttles are moved by atoms. There are two important factors: how many atoms are being used and how fast they are going. In space shuttle launches, the fuel flow rate at launch is about 10 tons a second. This means that for each second of the launch a space shuttle burns 10 tons of fuel. That's a huge amount of atoms! By contrast, Deep Space 1 will carry about 81.5 kilograms (179 pounds) of propellant total, and it will take about 20 months of thrusting to use all of that. That's millions of times fewer atoms. DS1 is able to make thrust using many millions fewer atoms for fuel because it accelerates them to a much higher speed before shooting them out.

How does DS1's engine work?
What is an atom?
Could ion propulsion move something on Earth?
Could NASA use ion propulsion to put a ship into space?
What is the difference between an ion engine and a conventional one?
How does propulsion work?

What causes ions to leave DS1?
What is thrust?

How is rocket propulsion different from jet propulsion?