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Diagnostic and imaging dental students

Diagnostic and imaging dental students

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Qi - Atom theory. Radiation
Atomic theory is the scientific theory that matter is composed of particles called atoms. The structure of the atom is key to the majority of the techniques used
in radiology
* Nucleus
~ Composition of an atom is principally ‘empty space5. Its mass is concentrated within the central nucleus which is composed of a specific number of nucleons
- Nucleons are either protons or neutrons, and the total number of nucleons is assigned the symbol A (also known as the mass number)
" The total number of protons within the nucleus is called the atomic number and assigned the symbol Z. Protons and neutrons are each assigned a relative mass of one
A: total number of nucleons = protons + neutrons (mass number)
Z: number of protons (atomic number)
- Protons and neutrons each consist of quarks and gluons
Two up quarks and one down quark form the proton
Two down quarks and one up quark form the neutron
Protons are positively charged
Neutrons have no charge
“ The atomic number always defines the element (it is the number of protons that determines that an atom (having 6 protons) is carbon
However more than one nuclide may exist for a given element (a carbon may exist with 6 neutrons or 8, these atoms of the same element with different numbers of neutrons are called isotopes: in each case there are still 6 protons)
4 electrons