The structural and electronic properties of the Ca_1-xNa_xV₂O₅ system, where the composition CaV₂O₅ exhibits an isolated dimer-like spin-gap state, and NaV₂O₅ indicates a linear-chain magnetic behaviour and undergoes a spin-singlet transition at T_c = 34 K, have been explored by means of x-ray four-circle diffraction and through magnetization and electron paramagnetic resonance measurements. The crystal structures with 0<x0.1 and 0.8 x1 are isomorphous with that of CaV₂O₅, where the space group is Pmmn. The effective V valence is correlated with the V-O bond length in the VO₅ pyramid, and the transfer integral for the next-nearest-neighbour V-V path is suggested to be larger than those for other paths, which may be consistent with the formation mechanisms of the dimer in the Ca-rich compounds and the V-O-V molecular orbital in the Na-rich compounds. The magnetic properties for 0<x0.1 are interpreted as being governed by contributions from the dimer which is formed between the V zigzag chains and from the isolated spins that are present due to the breaking of the dimer. On the other hand, the properties for 0.9 x<1 still exhibit linear-chain behaviours, and for x0.97 the singlet transition with a large reduction of the exchange coupling constant disappears, and no magnetic ordering takes place. The characteristic spin dynamics for the Na-rich compounds is also discussed