When we talk about radioactive decays, we will have 4 main types of decays:
1. Alpha decay: in this case, we have an atom losing 2 protons and 2 neutrons, therefore its atomic number will decrease by 2 and atomic mass will decrease by 4
2. Beta decay: in this case, we have a neutron turning into a proton and releasing an electron, therefore we will have an increase in the atomic number of the atom
3. Positron emission: similar case to number 2, but now, we have a proton turning into a neutron and we have the release of a positron, therefore in this case, we will have the atomic number down by 1
4. Gamma decay: In this case, we have changes in neither atomic number nor atomic mass, because we don't have the release of particles, but instead we have the release of gamma rays, which are a very radioactive type of rays
For the equation number 1, we have:
18/8 O -> 14/6 C + 4/2 He
For equation number 2, we have a neutron capture, this is a process to produce Plutonium 239, which starts with Uranium 238 capturing a neutron, becoming Uranium 239, after this, 239 U will go through Beta decay, where a neutron turns into a proton, and release an electron, therefore we will have Neptunium 239, 93 protons and 146 neutrons, Neptunium 239 will undergo another beta decay, and become Plutonium 239, 94 protons and 145 neutrons
238/92 U + 1/0 n -> 239/92 U
For equation number 3, we have:
18/8 O + 1/1 H -> 19/9 H