Start Radiochemical dating for chemistry

Radiochemical dating for chemistry

They help researchers find answers by allowing them to look at a problem in a new way, from a different perspective.

The numerical difference between the actual measured mass of an isotope and A is called the mass defect.

The specification of Z, A, and the chemical symbol (a one- or two-letter abbreviation of the element's name, say Sy) in the form A/ZSy identifies an isotope adequately for most purposes.

Many important properties of an isotope depend on its mass.

The total number of neutrons and protons (symbol A), or mass number, of the nucleus gives approximately the mass measured on the so-called atomic- mass-unit (amu) scale.

Thus in the standard notation, 1/1H refers to the simplest isotope of hydrogen and 235/92U to an isotope of uranium widely used for nuclear power generation and nuclear weapons fabrication. A "stable isotope" is any of two or more forms of an element whos nuclei contains the same number of protons and electrons, but a different number of neutrons.

(Authors who do not wish to use symbols sometimes write out the element name and mass numberhydrogen-1 and uranium-235 in the examples above.) Isotopes utilized in nuclear medicine fall into two broad categories: Stable and Unstable. Stable isotopes remain unchanged indefinitely, but "unstable" (radioactive) isotopes undergo spontaneous disintegration.

In some cases radiation can be used to treat diseased organs, or tumors.

In developed countries (26% of world population) the frequency of diagnostic nuclear medicine is 1.9% per year, and the frequency of therapy with radioisotopes is about one tenth of this.

The isotopes of an element have the same number of protons in their atoms (atomic number) but different masses due to different numbers of neutrons.

In an atom in the neutral state, the number of external electrons also equals the atomic number.

A bar of pure uranium, for instance, would consist entirely of atoms with atomic number 92.