Units 21 and 22: The Nuclear Atom and Radioactivity

We all know an atom is made of protons, neutrons, and electrons.

Protons and Neutrons make up the nucleus, while electrons orbit it.

from its name, we can tell that neutrons have a neutral charge. Protons have a positive charge, and electrons have a negative charge. Protons and neutrons have a relative mass of 1, electrons have a relative mass of 1/1836 (basically 0)

the gold foil experiment proved that the atom was mostly empty space, with a small positively charged nucleus.

Isotope: nuclei of the same element with different nucleon number (same proton number, more or less neutrons)

isotopes are usually unstable and decay

ion: same proton number, different electron number.

remember fission and fusion, they will come in handy later.

(fusion releases more energy)

(fission happens in nuclear reactors, fusion happens in stars)

Radioactive decay (decay of unstable isotopes)

We are surrounded by radiation know as background radiation.

Sources of background radiation:

There are three types of radioactive emissions: alpha, beta, and gamma.

in alpha decay, a helium nucleus is emitted, which has 2 protons and 2 neutrons.

in beta decay, an electron is emitted. remember to add 1 to the proton number of the original nuclei.

in gamma decay, gamma rays are emitted, with no change to the parent.

these are all types of ionising radiation, and can cause mutation of cells (cancer)

in order of most to least ionising:

alpha

beta

gamma

how to stop each type:

the half-life of a radioactive source is the time taken for half its radioactive nuclei to decay. (count rate to halve)

the device used to detect radiation is called a Geiger counter.

regarding the deflection of alpha and beta particles, beta particles deflect more as they are lighter.

That's it for now. It is important to note that I have omitted certain details to make this as concise and helpful as possible. If there is something I have not covered here, please leave a comment on the forums.