<span>A half-life of a radioactive substance is the amount of time needed for one hald of the nuclie in a sample to decay into a stable isotope.Many protons and neutrons disturb the balance of binding energy from a strong nuclear forces resulting for the nucleus to be unstable. To be in a balance state, the unstable nucleus will give off a proton or neutron through radioactive decay.</span>
What percent of potassium-40 remains undecayed in a rock that is 3.9 billion years old? The 3.9 billion year old rock has undergone three half-lives (3.9 divided by 1.3 = 3). After 3 half-lives, 12.5% of the potassium-40 remains undecayed.
DNA is located in the nucleus, but can also be found in other cell structures called mitochondria. Since the nucleus is so small, the DNA needs to be tightly packaged into bundles known as chromosomes.
