The Minor Scale
C to D is one whole step due to the black key in between them. D to Eb is one half step there are no keys between them.
The Minor Scale can be thought of as whole step - half step - whole step - whole step - half step - whole step - whole step.
Try to remember this pattern.
Another way to think of the notes is in numbers - the first note C=1 and the second note D=2 and the third note in the scale Eb=3 and so on. Please have a look at Diatnic Harmony to see how the numbers way is the best in the end.
How to play a Minor Chord and the Piano.
By Michael Pelletier