Atoms and Radiation

(GCSE physics)
Atoms radiate when they are unstable. Radiation is spontaneous and unpredictable and can take four forms;

• Alpha Radiation
• Beta Radiation
• Gamma Radiation 
• Neutron Radiation (this is not one of the main three but can be considered a form of radiation as it is spontaneously emitted)

 (Greyson Joralemon)

Alpha radiation is the emission of an alpha particle, which is the equivalent to a nucleus of a helium (2 protons and 2 neutrons). As the two protons and two neutrons are lost, the element changes. The atomic number reduces by 2 and the atomic mass reduces by 4. Alpha radiation is the most ionising and least penetrative form of radiation. As it's the least penetrating, it can be stopped by thin materials like paper.It can cause the most problems inside the body because it's the least penetrating so once it enters the body, it struggles to leave and the ionisation can cause many issues like mutations and potentially cancer. 

However, it can also be used for good too. Alpha radiation is used in the detection of smoke in smoke alarms;

• A constant source of radiation is placed near the detection of the radiation
• If smoke particles are present, they will block the direction of the alpha particles
• The detector detects a change in the radiation source and sounds the alarm
• Its important that a source with a long half-life is used so that the radiation will be continuous

Beta radiation is the emission of electrons from a source. In the nucleus of the unstable element, which are often because an isotope has a strange number of neutrons, a neutron will split into a proton and an electron. The proton will embed in the nucleus and the electron is emitted. Due to this, the element's atomic number will increase by 1 but the element's atomic mass remains the same because no particles (apart from very very light electrons) are lost. Beta decay is less ionising than alpha and more ionising than gamma. It is also more penetrating than alpha but less penetrating than gamma. Beta decay can be stopped by a thin sheet of aluminium foil. 

Beta decay radiation can be used in paper manufacturing;

• Beta particles are constantly fired through the produced paper at a detection screen behind
• If the paper is too thin or thick, more or less particles will transfer through the paper to the detector and the machine can process this change and stop.

Gamma Radiation is the emission of electromagnetic gamma rays from an unstable element. This is a transfer of extra energy from the element however, the element doesn't change because no subatomic particles (protons, neutrons and electrons) are lost. Gamma radiation is the most penetrating and least ionising form of radiation and can only be stopped by a thick layer of concrete or lead. 

It can be used in many ways;

• Medical Sterilisation- gamma rays are strong enough to kill bacteria and microorganisms so can be used to clean scientific and medical equipment
• Organ Screening- a radioactive source that emits gamma radiation can be consumed so that it can emit radiation for a monitor to detect to create an image of the organ/blood. It's important this source has a short half-life so that it does minimal damage (Example include Iodine 123 and Iodine 131)

Although an individual atom's radiation is unpredictable, a group of atoms of an element can behave similarly and we can predict the nature of an element's decay. We use a measure called a Half-life. A Half-Life is the time taken for half of an isotope's nuclei to decay. For example if Uranium loses half of its nuclei in 200 days then we can say that the half life of Uranium is 200 days. This would mean that after another 200 days, we would have a quarter of the original nuclei and then after 200 more days, an eighth of the original etc. Some elements can have half-lives of seconds or thousands of years.

When studying atoms, we must also look at fusion and fission- which are very different things! Fission is the splitting of one large nucleus into two smaller, daughter nuclei. Fission occurs when a high-energy neutron collides with a large nucleus causing it to release high amounts of energy, two or three neutrons and two smaller, daughter nuclei. The two or three neutrons released will almost always be released at high velocity and high energy and these can go on to react with other large nuclei. When the neutrons collide with large nuclei to release more neutrons that collide, this is called a chain reaction as they continue to cause more and more reactions. Possible sources of unstable isotopes include Uranium 235 and Polonium.

As reactions occur, lots of energy is released which can be used in nuclear power stations to heat water, produce steam, turn turbines and generators and generate electricity. Additionally, fission reactions can be used in A-bombs (atomic bombs) as the fission reactions release high amounts of energy and chain reactions can easily get out of control.

Fusion reactions, however, are very different to fission reactions. Fusion is the joining of two smaller nuclei in order to form one larger nucleus. This process also releases energy (our sun carries out fusion which is how we get the heat/energy from the sun) but scientists cannot use this method to produce electricity because the conditions required (really high temperature and pressure) are too difficult to achieve. Fusion reactions can be used in H-bombs (hydrogen bombs) which release lots of energy.