The representations of the group lie in the 2-dimensional I 3 − Y plane. Here, I ^ ^ 3 stands for the z-component of Isospin and Y ^ ^ is the Hypercharge, and they comprise the (abelian) Cartan subalgebra of the full Lie algebra. The maximum number of mutually commuting generators of a Lie algebra is called its rank : SU(3) has rank 2. The remaining 6 generators, the ± ladder operators, correspond to the 6 roots arranged on the 2-dimensional hexagonal lattice of the figure.