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The ground state of the three-proton emitter 17Na has been identified. Energy correlations between the protons and the 14O residue indicate that its decay is sequential initiated by the emission of a single proton to the ground state of 16Ne followed by simultaneous emission of two protons to the ground state of 14O, and the derived total decay energy is 4.45(3) MeV. The angular distribution of the proton from the first step indicates that this emission is d-wave and only consistent with a spin parity of 5=2þ. This assignment is consistent with state-of-the-art Gamow shell-model calculations. As the ground state of 17C is 3=2þ, the assigned spin parity of its mirror 17Na indicates that the pair presents a new case of ground-state mirror symmetry violation (GMSV). Unlike other GMSV cases, which arise solely from either a Coulomb induced shift or deformation effects, the 17Na=17C case is generated by differences in the many-body correlations. 

The boundaries of the Chart of Nuclides contain exotic isotopes that possess extreme proton-toneutron asymmetries. Here we report on two of the most exotic proton-rich isotopes where at least one half of their constitute nucleons are unbound. While the ground state of 8C is a resonance, its first excited state lies in the diffuse borderland between nuclear states and fleeting scattering features. Evidence for 9N, with seven protons and two neutrons, is also presented. This extremely proton-rich system represents the first-known example of a ground-state five-proton emitter. The energies of these states are consistent with theoretical predictions of an open-quantum-system approach.