There is no going back – the process is irreversible. When we pour our popcorn kernels into a popcorn popper, the is no way to know which will pop first.
If they can begin to comprehend that it is random and spontaneous, they end up feeling less nervous about the whole thing.
Radioactive decay involves the spontaneous transformation of one element into another.
The only way that this can happen is by changing the number of protons in the nucleus (an element is defined by its number of protons).
There are a number of ways that this can happen and when it does, the atom is forever changed.
Radioactivity and radioactive decay are spontaneous processes.
Students often struggle with this concept; therefore, it should be stressed that it is impossible to know exactly when each of the radioactive elements in a rock will decay.
Statistical probablity is the only thing we can know exactly.
Often students get bogged down in the fact that they don't "understand" how and why radioactive elements decay and miss the whole point of this exercise.
Isotopes of an element are atoms that all have the same atomic number (or number of protons in the nucleus) but have different atomic masses (hence different numbers of neutrons in the nucleus).
For example, all atoms of oxygen have 8 protons in the nucleus and hence have an atomic number of 8.
However, oxygen atoms can have between 8 and 10 neutrons in the nucleus and therefore the isotopes of oxygen have atomic masses of 16, 17, and 18 a.m.u.(and none are radioactive! Samarium (Sm) has 7 naturally occurring isotopes (3 are radioactive).