Final answer:
The second movement of Mozart's Symphony No. 40 is in sonata form, features staccato rhythmic motives, and has a melancholic mood.
Step-by-step explanation:
Mozart's Symphony No. 40 in G Minor, K. 550, II is written in a sonata form, which is generally structured with an exposition, development, and a recapitulation. The main rhythmic motive of the movement introduced by the violins is played staccato, which means with each note sharply detached or separated from the others.
The mood of this movement is best described as melancholic. It has a sorrowful and pensive character which complements the overall minor key of the symphony, contributing to a feeling of internal unease or contemplation.