Final answer:
A twelve-tone scale with all the semitones of the octave is known as a chromatic scale, which is different from a diatonic scale and includes twelve distinct pitches before reaching the octave.
Step-by-step explanation:
A twelve-tone scale that includes all the semitones of the octave is called a chromatic scale. This scale differs from the diatonic scale, which consists of five whole steps and two half steps, and doesn't use every semitone. The chromatic scale includes every semitone within an octave, making it a scale of twelve distinct pitches before reaching the octave, which is the same note as the starting pitch, but at a higher pitch level. It is commonly used in Western music to create tension or to modulate to different keys.