The final discussion topic has three parts and is about nuclear physics. Some background information first. By the way, there will be a few questions on the final exam about this background information.

The modern theory of the atom is that the atom consists of a nucleus of protons and neutrons. Electrons surround the nucleus not as particles orbiting the nucleus, but as standing matter waves like the standing waves on a guitar string that has been plucked. As such, there location is not precisely known. Most of the atom is empty space. The total energy of an electron in an atom is quantized meaning it has certain discrete energy values such as 1 or 2 or 3 energy units, but nothing in between like 1,23 or 2.76 energy units. When an electron in an atom has a transition (i.e. falls) from a higher energy state to a lower energy state, the atom can give off a particle of light called a photon.

With regards to the nucleus, if the ratio of the number of neutrons to the number of protons is greater than about 1. The nucleus is unstable. First, the three main decay products of an unstable or radioactive nucleus are alpha particles, beta particles, and gamma rays. Alpha particles are just the nucleus of a helium atom (2 protons and 2 neutrons). They do not penetrate very far. Dead skin or a sheet of paper can stop them. Beta particles are electrons and can penetrate a thin layer of steel. A 1-cm thick piece of plastic can stop them. Gamma rays are high-energy photons and are very penetrating.

If a radioactive isotope that emits alpha particles is ingested, the living tissue stops them and absorbs their energy. Smoke detectors contain a radioactive isotope that emits alpha particles.

Discussion Topic

Part 1: Are smoke detectors safe?

Part 2: Radon gas is an inert gas that is not toxic or poisonous, but is radioactive and emits alpha particles. Why is radon dangerous?

Part 3: What are the advantages and problems with nuclear energy?

each question 50 to 100 words… relate to physics as this is a physics class