Bromine (Br), at atomic number 35, has a greater variety of isotopes. There are two main isotopes at 79 and 81, which average out to the 79.90amu value. While it won't change the average atomic mass, scientists have made bromine isotopes with masses from 68 to 97. As you move to higher atomic numbers in the periodic table, you will probably find even more isotopes for each element.
Half-life is constant over the lifetime of an exponentially decaying quantity, and it is a characteristic unit for the exponential decay equation.
The accompanying table shows the reduction of a quantity as a function of the number of half-lives elapsed.
There is a time when it loses its extra neutrons and becomes C-12.
The loss of those neutrons is called radioactive decay. For carbon, the decay happens in a few thousand years (5,730 years).
Note the consequence of the law of large numbers: with more atoms, the overall decay is more regular and more predictable.
A half-life usually describes the decay of discrete entities, such as radioactive atoms.
In that case, it does not work to use the definition that states "half-life is the time required for exactly half of the entities to decay".
For example, if there is just one radioactive atom, and its half-life is one second, there will not be "half of an atom" left after one second.
We have already learned that ions are atoms that are either missing or have extra electrons. They are just a little different from every other atom of the same element. Electrons don't have much of a mass when compared to a neutron or proton.
Let's say an atom is missing a neutron or has an extra neutron. An atom is still the same element if it is missing an electron. For example, there are a lot of carbon (C) atoms in the Universe. Atomic masses are calculated by figuring out the amounts of each type of atom and isotope there are in the Universe.
The average atomic mass for the element is actually 12.011.