C7 chord for piano with the piano diagram.
The C7 or C dominant 7th Chord is a tetrad, meaning it contains four notes. Also the shaded area in the piano diagram has four notes shaded is the chord.
The C dominant 7th chord is constructed with a root, major 3rd (third), major fifth (5th) and minor seventh (7th).
Left hand: 5-4-3-2 Right Hand: 1-2-3-5