How can alpha decay be reduced

Protons are positively charged. When a nucleus emits an alpha particle, these changes happen:. Radon decays into polonium by emitting an alpha particle. This is the balanced equation for the reaction:. Notice that:. Alpha decay a. An alpha particle is identical to the nucleus of a helium atom.

All nuclei with an atomic number Z greater than 82, are considered unstable. Alpha decay occurs in the nuclei of heavy elements, like radium, uranium, thorium, etc.

When a nucleus of Ra radium decays, it emits an alpha particle and becomes an Rn radon nucleus. In general, during alpha decay, the atomic number Z is reduced by two, and the mass number A , by four. For example, alpha decay generates Rn with atomic number 86 and the mass number from Ra with the atomic number 88 and the mass number Alpha particles are very heavy and contain high amounts of energy MeV.

They usually pass short distances a 5 MeV alpha particle will travel about 20 micrometers in silicon and can be stopped by a sheet of paper. Alpha particles do not produce Bremsstrahlung radiation when slowing down. Alpha particles are not generally dangerous unless the source is ingested or inhaled since alpha radiation is the most destructive form of ionizing radiation.

Historically, radium and radon were the principal alpha emitters of medical interest. Radium dichloride is still used today in treating osseous metastases. Their massive size compared to beta particles, for instance means alpha particles have very low penetration power. Penetration power describes how easily the particles can pass through another material. Since alpha particles have a low penetration power, the outside layer of the human skin, for example, can block these particles.

Alpha decay occurs because the nucleus of a radioisotope has too many protons. A nucleus with too many protons causes repulsion between these like charges. Examples of this can be seen in the decay of americium Am to neptunium Np. In radioactive nuclei with too many neutrons, a neutron can be converted into an electron, called beta particle. During beta decay, the number of neutrons in the atom decreases by one, and the number of protons increases by one.

Effectively, a neutron was converted into a proton in the decaying nucleus, in the process releasing a beta particle. Some decay reactions release energy in the form of electromagnetic waves called gamma rays. However, unlike visible light, humans cannot see gamma rays, because they have a much higher frequency and energy than visible light. The top number, 4, is the mass number or the total of the protons and neutrons in the particle.

Because it has two protons, and a total of four protons and neutrons, alpha particles must also have two neutrons. Alpha particles always have this same composition: two protons and two neutrons. These types of equations are called nuclear equations and are similar to the chemical equivalent discussed through the previous chapters. Another common decay process is beta particle emission, or beta decay.

A beta particle is simply a high energy electron that is emitted from the nucleus. It may occur to you that we have a logically difficult situation here. Nuclei do not contain electrons and yet during beta decay, an electron is emitted from a nucleus. At the same time that the electron is being ejected from the nucleus, a neutron is becoming a proton. It is tempting to picture this as a neutron breaking into two pieces with the pieces being a proton and an electron.

That would be convenient for simplicity, but unfortunately that is not what happens more on this subject will be explained at the end of this section. For convenience, we will treat beta decay as a neutron splitting into a proton and an electron.

The proton stays in the nucleus, increasing the atomic number of the atom by one. The electron is ejected from the nucleus and is the particle of radiation called beta. To insert an electron into a nuclear equation and have the numbers add up properly, an atomic number and a mass number had to be assigned to an electron.

The mass number assigned to an electron is zero 0 , which is reasonable since the mass number is the number of protons plus neutrons, and an electron contains no protons and no neutrons. The atomic number assigned to an electron is negative one -1 , because that allows a nuclear equation containing an electron to balance atomic numbers. Therefore, the nuclear symbol representing an electron beta particle is. Thorium is a nucleus that undergoes beta decay.

Here is the nuclear equation for this beta decay:. Frequently, gamma ray production accompanies nuclear reactions of all types. Virtually all of the nuclear reactions in this chapter also emit gamma rays, but for simplicity the gamma rays are generally not shown. Nuclear reactions produce a great deal more energy than chemical reactions. Nuclear reactions release some of the binding energy and may convert tiny amounts of matter into energy.

That means that nuclear changes involve almost one million times more energy per atom than chemical changes! Figure Confirm that this equation is correctly balanced by adding up the reactants' and products' atomic and mass numbers. The mass numbers of the original nucleus and the new nucleus are the same because a neutron has been lost, but a proton has been gained, and so the sum of protons plus neutrons remains the same. The atomic number in the process has been increased by one since the new nucleus has one more proton than the original nucleus.

In this beta decay, a thorium nucleus has one more proton than the original nucleus.