They are evenly distributed as alternating pairs of past and future around the zodiac circle. Each element has three signs that are always 120 apart to create four triplicities. This arrangement creates pairs of duality, triplets of elements and quardranties of the crosses of cardinal, fixed and mutable. These are patterns of geometry of which astrology is a branch of mathematics applied to life. The three Water elements represent our basic emotions.
Cancer means individual survival or fear of starvation.
Scorpio represents the procreation of the family or the sex drive. Pisces stands for social survival or our need to belong to a group. Each element is opposed by its opposite. The Water signs are opposed by Earth signs. The element Earth represent the holding back of the emotions or the containment of the instincts.