Rutherford's Scattering Experiment
At the start of the 20th century, Ernest Rutherford devised an experiment to investigate the structure of atoms.
Positively-charged alpha particles were fired at a very thin piece of gold foil in the apparatus shown below. Because of the vacuum, the alpha particles were able to travel freely.
Every time an Alpha particle hit the fluorescent screen, the screen glowed for a short time. The microscope was moved all around the outside of the circular fluorescent screen, so that the number of alpha particles hitting the screen at every position could be observed.
The video below explains the observations Rutherford's team recorded.
Rutherford deduced 3 main points about atoms from these results:
1. Because most of the positively-charged alpha particles passed straight through the gold atoms in the foil, most of the atom must be empty space.
2. Because only very, very few positively-charged alpha particles were deflected backwards in almost the direction they had come from, most of the mass of the atom must be concentrated in a very small central area.
3. Because some of the positively-charged alpha particles were deflected backwards by the nucleus, the nucleus must be positively-charged.
Because of these findings we can deduce the atom's structure:-
Proton - Positive charge (+1), mass of 1 Atomic Mass Units (A.M.U.).
Neutron - No charge (0), mass of 1 Atomic Mass Units (A.M.U.).
Electron - Negative charge (-1), mass negligible.
The diagram below shows a summary of the history of the structure of the atom:-
Radioactivity and Decay
The symbol for an atom is often written in the form:-
There are three types of radioactivity that can be emitted from atomic nuclei during radioactive decay:-
1. Alpha particles.
2. Beta particles.
3. Gamma rays.
Alpha decay takes place when an alpha particle (consisting of 2 protons plus 2 neutrons) is ejected from an atom's nucleus.
Beta decay takes place when a neutron in the nucleus decays into a proton and an electron. The proton stays in the nucleus (so the atomic number increases by 1) while the electron is ejected from the atom's nucleus as a beta particle.
Gamma rays are photons of electromagnetic energy - They are not particles. When gamma rays are ejected from an atom's nucleus, this does not change the mass number or atomic number of the atom. It does however change the energy state of the nucleus.
When one of the three types of radiation is incident (hits) another atom, the radiation can cause ionisation, which removes an outer electron from the nucleus, creating an ion.
Each type of radiation ionises matter by different amounts, and this affects how far the radiation can travel through a material, the more ionising the radiation, the shorter its range:-
The video below gives a brief summary of Nuclear Radiation and decay:-
The diagram below shows a summary of the Three types of Radioactive Decay:-
You would use different kinds of radiation to help diagnose or treat people who are ill or injured.
You would use highly technical, computerised equipment. There are two types of radiography – diagnostic and therapeutic.
As a diagnostic radiographer, you would; Produce and interpret high quality images of the body to identify and diagnose injury and disease, screen people for abnormalities or take part in surgical procedures, such as biopsies (examining tissues to find the cause of disease).
As a therapeutic radiographer, you would; plan and deliver treatment using x-rays and other radioactive sources, work closely with medical specialists to plan and treat malignant tumours or tissue defects or assess and monitor patients throughout treatment and follow up.
Your patients might be very anxious and upset so you’d need to be sensitive and gentle with them.
In both areas you would work as part of a team with radiologists, clinical oncologists, physicists, radiology nurses and other healthcare professionals.
Your patients could be very ill; you’d need to have emotional strength. It would also be important to keep up to date with new techniques and treatments.
Working as a Radiographer
Training to be a RADIOGRAPHER
A Career as a Radiographer
Salary: from £35,000 to £51,000 per year
Radiographer working hours: 37 hours a week, which may include shifts and unsocial hours (such as evenings, weekend and public holidays).
Typical entry requirements: You need an honours degree in radiography (SCQF level 10).
To entry a radiography honours degree (SCQF level 10) requires National 5 qualifications and at least four Highers at BBBC or above.
To enter a two-year postgraduate diploma (SCQF level 11) which can lead to an MSc course in Radiotherapy, you will need a relevant science or health related honours degree
Working with numbers
Developing a plan