Now that you have an understanding of intervals, accidentals and some other fundamental concepts about music, we can put that information to use as we learn about SCALES which are of primary importance in the realm of tonal music. The term SCALE refers to a stepwise arrangement of pitches in ascending or descending order spanning an octave. There are several types of SCALES. A few are named below (POINT YOUR MOUSE at the question mark to see what each looks like).
PENTATONIC SCALE 
CHROMATIC SCALE
OCTATONIC SCALE
DIATONIC SCALE
Notice that each each SCALE contains a different arrangement of intervals between each note of the SCALE. The intervallic relation of notes in a SCALE provides a unique character to that SCALE. Our current concern is that of DIATONIC SCALES.
When you POINT YOUR MOUSE at the above DIATONIC SCALE example, you should notice several things: 1) The notes are stepwise (alphabetically) ascending. They may also be descending. 2) All the basic notes are represented including the octave duplication. No notes are missing. 3) Eight notes are required for a complete, one-octave DIATONIC SCALE.
