Atomic structure, isotopes, radioactive decay, photons and PET applications

Apuntes

AQA Physics A-level Section 2: Particles and Radiation Notes www.pmt.education 3.2.1 Particles 3.2.1.1 - Constituents of the atom An atom is formed of 3 constituents: protons, neutrons and electrons. At the centre of an atom is a nucleus formed of protons and neutrons, therefore they are known as nucleons, whereas electrons orbit the nucleus in shells. These particles have properties which can be described in two ways, in SI units and relative units, as shown below: Particle Charge (C) Relative Charge Mass (kg) Relative Mass Specific Charge (Ckg -1 ) Proton .6 ✕ 10+ 1 −19 +1 .67 ✕ 101 −27 1 .58 ✕ 109 7 Neutron 0 0 .67 ✕ 101 −27 1 0 Electron .6 ✕ 10− 1 −19 -1 .11 ✕ 109 −31 0.0005 .76 ✕ 101 11 The specific charge of a particle is the charge-mass ratio, and is calculated by dividing a particle’s charge by its mass. For example: A proton has a charge of , and a mass of kg..6 ✕ 10 C+ 1 −19 .67 ✕ 101 −27 So its specific charge = 1.6×10 −19 1.67 ✕ 10 −27 .58 0 Ckg= 9 × 1 7 −1 The proton number is the number of protons in an atom and is denoted by , while theZ nucleon number is the number of protons and neutrons, denoted by . These will often beA shown in the form: where ‘X’ is the symbol ...