31:3 · This ideogram is a graphic model of the current theory of the organization of matter on the microcosmic level. The point in the middle denotes the nucleus of the atom, and the ovals indicate the orbital paths of the invisible electrons. The model is presented in an imagined three-dimensional space (suggested by the asymmetry). The sign is a symbol for uranium, nuclear power, nuclear physics, and related areas.
    Compare with , a sign from Ghana, Africa.
    The signs and in Group 25 are synonymous and much more common.