Pwyll Pendefig Dyfed

An isotope means it has the same number of protons (i.e. atomic number - which defines it as that element) but the number of neutrons (and hence the atomic mass) varies. For example there are three isotopes of Hydrogen. Each has an atomic number of 1. One isotope has an atomic mass of 1 (1 proton, 0 neutrons), another isotope (deuterium) has and atomic mass of 2 (1 proton, 1 neutron); the third isotope (tritium) has an atomic mass of 3 (1 proton, 2 neutrons).

Aren't Energy and mass linked? According to E=mc2 they are.

In terms of the electrons, it looks correct. Mn2+ --> MnO4- is going from +2 (due to it's charge) to +7, so it's being oxidised. NaBiO3 --> Bi3+ (like in the previous question) is going from +5 to +3, so it's being reduced. The Na and H remains at +1, the O remains at -2 The oxygens in the MnO4 and in H2O2 will be oxidised, as they're forming O2. All the oxygens are losing electrons, so they're all being oxidised.