Transistor and resistor

Projects General Guidance
1

I have a small transistor a 2n2222. It has a 100 ohm resistor to Arduino. I plugged in a small fan (only 80 Ma at 5 volts) to the transistor. When connected to the resistor it does not go as fast as when I connect it to +5 line

2

It has a 100 ohm resistor to Arduino.

That is too small use 1K or so.

When connected to the resistor it does not go as fast as when I connect it to +5 line

Yes it won't because of the saturation voltage drop across a transistor.
Also I hope the load is in the collector and not the emitter.

3

the load should be in the collector? what happens if they are switched?

4

Then you get even more loss of voltage through the transistor.

5

(only 80 Ma at 5 volts)

sp. "mA"