Radiation

Radiation comes from the nucleus, nucleus consists of protons and neutrons. Protons are positively charged while the neutron is neutral. Elements(except helium) always have protons and neutrons which are called nucleons. We can describe how they are by using the atomic number. Any two nuclei that have the same atomic number but different mass numbers are known as isotopes. Most carbons in the world are C-12, only a little is C-14 because carbon is the most stable when the number of protons equal the number of neutrons. If a nuclei is unstable then they are radioactive, nuclei are held together by strong nuclear force(an attractive force that acts between protons and nucleus in a nucleus) this force is strong enough to overcome the repulsive attraction between protons. 

The decay of unstable nuclei is called radioactivity. Three different groups based on their penetrating power, alpha decay(released when an unstable nucleus loses 2 protons and neutrons, turning into a new element, also the lowest penetrating power) first it is there is an unstable nucleus which then decays into a stable nucleus and a alpha particle which is just helium, this occurs because the unstable nucleus is too large and the strong force is no longer sufficient to hold it together. The process of a nucleus changing into another element is called transmutation. The products of these reaction masses are turned into kinetic energy and then released to generate nuclear power. Beta decay (when an unstable nucleus emits electrons) beta decay is caused by the weak force(alters quarks) that converts neutrons into protons. Gamma decay(happens when a nucleus emits gamma rays) occurs when a nucleus is in an excited state which can happen because the nucleus is decaying from a larger form, or it collided with a high energy particle. When a nucleus is excited, it wants to transition into a lower energy state, no transmutation occurs in gamma decay, instead the excited nucleus just decays into ground state nucleus and a gamma ray , highest penetrating power, needs a large amount of lead and concrete. 

Activity is the overall rate of decay of all the isotopes in our sample and we can measure it using becquerels where 1bq = 1 decay per second. Half life is the time taken for the no. of radioactive nuclei in a sample to halve or the time taken for the no. of the decays of activity to halve, this process is also very hard to predict and it is random . When more and more unstable nuclei are decaying than the number of unstable particles decreases, since there are more and more decaying than the overall rate of decay also decreases, this is how we define half life. We can calculate the half life of an element by using a graph. 

Ionising radiation(Beta, alpha and gamma) enter living cells and interact with the molecules inside, the radiation can ionise our DNA which can cause mutation, in rare cases cells can divide uncontrollably and then lead to cancer(ultraviolet radiation can also lead to cancer). The order(inside/on the body) for ionising is Alpha,Beta and then Gamma. (Outside) Gamma, Beta and then Alpha. Alpha cant penetrate the skin while beta and gamma can, however inside/on your body then alpha is the most harmful because it can make it into your cells.

Large doses of radiation can kill cancer, radiation sickness happens when you get a large dose of radiation throughout your whole body, which can lead to vomiting, tiredness, and hair loss, loads of your cells can be either destroyed or badly damaged. Radiation can cause and kill cancer and treat cancer. This process is called radiotherapy, two main ways that we can deliver the radiation externally or internally. External sources emit gamma rays that are targeted at the cancer site from lots of different angles, so only the cancer site gets the highest dose. Internal method is where we place radioactive source inside the body either inside the cancer itself or next to the cancer, this method uses beta radiation which is more damaging than gamma rays but cant pass as far through the body. Both of these techniques have side effects, other healthy cells will also get damaged or killed in the process which is why cancer therapy make people sick