One of two or more atoms which have a common mass number A but which differ in atomic number Z. Thus, although isobars possess approximately equal masses, they differ in chemical properties; they are atoms of different elements. Isobars whose atomic numbers differ by unity cannot both be stable; one will inevitably decay into the other by β^- emission (Z→Z + 1), β⁺ emission (Z → Z – 1), or electron capture (Z →Z − 1). There are many examples of stable isobaric pairs, such as ⁵⁰Ti (Z = 24) and ⁵⁰Cr (Z = 26), and four examples of stable isobaric triplets. At most values of A the number of known radioactive isobars exceeds the number of stable ones.