Half life radioactive dating
C and counting the amount of each) allows one to date the death of the once-living things.
Half of 50% is 25%, so you would have 25% Carbon-14 and 75% Nitrogen-14.
In other words, half (50%) of the Carbon-14 you started with has decayed into the daughter isotope Nitrogen-14.
However, your readout from your radioactivity measuring instrument says you have only 25% Carbon-14 and 75% Nitrogen-14, so your fossil must have been through more than one half-life.
Below is a chart of commonly used radiometric isotopes, their half-lives, and the daughter isotopes they decay into.
Let's say you found a fossil you think to be a human skeleton.
As radioactive isotopes of elements decay, they lose their radioactivity and become a brand new element known as a daughter isotope.