Chapter 13 Assessment Exercises

No radioactivity in the world is not something that is relatively new. The sun has been blowing radioactive particles into space from the beginning of its concept and a lot of it has always been scattering all over the earth.

Radioactive material is always undergoing decay. Radioactive elements decaying; basically there constantly breaking down into other energy forms. During this process energy is released, mainly in the form of heat, which is why it is usually warmer than the surrounding. When a substance releases energy, it is known as an Exothermic reaction.

It is not possible since a hydrogen nucleus is only a single proton and an alpha particle is a helium nuclecus containing two protons and two neutrons. A hydrogen nucleus just doesn't have enough particles to give off alpha radiation.

Alpha particles are helium nuclei which carry 2 positive charges Beta rays are electrons which carry a negative charge. Hence the magnetic forces are in opposite directions. Gamma rays are propagating EM waves (photons) which are not subject to magnetic forces since they are electrically neutral and travel in straight lines.

The protons repel one another. The repulsion keeps slow protons from getting close to the nucleus. The strong nuclear force can overcome the repulsion but it is only active over very short distances. You need to shoot the protons fast enough that they can overcome the repulsion of the nuclear protons and get close enough to be captured by the strong force.

Protons are able to exist side by side in an atomic nucleus

A lot of the energy created by nuclear fission is uncontrollable, and there is far too much energy produced which would cause other problems such as melting the car for instance. It could be used indirectly by simply supplying power to car batteries, that is to say, electric cars running off power generated by nuclear fission.

If it is to penetrate the nucleus, clearly a proton has the handicap of its positive charge. Like charge repel, all the more strongly that they are close. So the proton closing in on a nucleus will be scattered in another direction and hit the nucleus only if it is very energetic. The electron has the opposite charge, so it is not the problem. But it is much lighter and clearly you cannot replace a roller ball by a ping pong ball and hope for a strike. Also, it has no strong interactions and will influence the nucleus only through its electric charge. The neutron has no charge and the same mass as the proton and it has strong interactions, so it is clearly much fitter.

Isotopes of Uranium will continue to radioactively decay until reaching a stable state. One of those isotopes decay to lead.

The density of fissionable uranium is not high enough. Basically more neutrons are absorbed than are produced so any chain reaction dies.

When Th 232/90 absorbs a neutron, the atomic mass increases but the atomic number stays the same, so that produces 233/90 Th. If that nucleus undergoes beta decay, the neutron becomes a proton and emits an electron; this increases the atomic number by one but does not change the atomic mass, so the first decay produces Pa 233/91. The second beta decay increases the atomic number by one, so you get U 92/233 which is Uranium-233.

The mass of the nucleons is the same, but their binding energy is different. This means (via E=mc^2) that the mass of the fragments do not add to the mass of the uranium nucleus, because some of the mass arises from the binding energy.

Nuclear binding energy is at its maximum for Iron. In practical terms, neither fission nor fusion processes would release nuclear energy from Iron. Gold has greater atomic mass than Iron, so would release nuclear energy in fission processes. Carbon has lighter atomic mass than Iron, so would release nuclear energy in fusion processes.