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To determine which elements are present in the ionic compound, we need to analyze the ions formed when it dissolves in water.
According to the given equation, the ionic compound MA2 breaks down into the M^+2 and A^- ions.
Since the ground state electron configuration of both ions is similar to that of neon (Ne) and krypton (Kr), we can conclude that the element M corresponds to the electron configuration of Kr (similar to Kr: [Kr]5s^24d^105p^6), while the element A corresponds to the electron configuration of Ne (similar to Ne: [He]2s^22p^6).
Therefore, M represents the element krypton (Kr) and A represents the element neon (Ne).