# Differentiate carbon dating uranium dating

The half-life of a radioactive nuclide is defined as the time it takes half of a sample of the element to decay.A mathematical formula can be used to calculate the half-life from the number of breakdowns per second in a sample of the nuclide.

So an atom of potassium-40 (K40), atomic number 19 can absorb an electron to become an atom of argon-40 (Ar40), atomic number 18.Some nuclides have very long half-lives, measured in billions or even trillions of years.Others have extremely short half-lives, measured in tenths or hundredths of a second.Since all atoms of the same element have the same number of protons, different nuclides of an element differ in the number of neutrons they contain.For example, hydrogen-1 and hydrogen-2 are both nuclides of the element hydrogen, but hydrogen-1's nucleus contains only a proton, while hydrogen-2's nucleus contains a proton and a neutron.The decay rate and therefore the half-life are fixed characteristics of a nuclide. Thats the first axiom of radiometric dating techniques: the half-life of a given nuclide is a constant.

(Note that this doesnt mean the half-life of an element is a constant.

Thats the essence of radiometric dating: measure the amount thats present, calculate how much is missing, and Obviously, the major question here is "how much of the nuclide was originally present in our sample? If an element has more than one nuclide present, and a mineral forms in a magma melt that includes that element, the elements different nuclides will appear in the mineral in precisely the same ratio that they occurred in the environment where and when the mineral was formed. The third and final axiom is that when an atom undergoes radioactive decay, its internal structure and also its chemical behavior change.

Losing or gaining atomic number puts the atom in a different row of the periodic table, and elements in different rows behave in different ways. C14 is radioactive, with a half-life of 5730 years.

The rules are the same in all cases; the assumptions are different for each method.

To explain those rules, I'll need to talk about some basic atomic physics. Hydrogen-1's nucleus consists of only a single proton.

Uranium-238 contains 92 protons and 146 neutrons, while uranium-235 contains 92 protons and 143 neutrons.