3.2 Particles and Radiation
3.2.1 Particles
3.2.1.1 Constituents of the Atom
● Overall neutral charge
● Mass concentrated in nucleus
● Nucleus made from protons + neutrons (nucleons)
● Electrons exist in energy levels around nucleus
Charge (C) Mass (kg) Relative Mass Relative Charge
Proton +1.6 x 10-19 1.67 x 10-27 1 +1
Neutron 0 1.67 x 10-27 1 0
Electron -1.6 x 10-19 9.11 x 10-31 ≈ 1\2000 -1
Electrons
● DO NOT orbit nucleus like planets around a sun
● Seemingly pop in and out of existence
● Higher probability that an electron will exist in an energy level
Ions
● Charged atom
● Atom loses or gains electrons (loses = +ve charge, gains = -ve charge)
Isotopes
● Atoms of the same element (same number of protons)
● Different number of neutrons (so different mass)
Symbols
● A - mass number
● Z - atomic (proton) number
, Specific Charge
● Specific = per kg (per unit mass)
charge
● S pecif ic Charge = mass
● Measured in C kg-1 (coulombs per kg)
3.2.1.2 Stable and Unstable Nuclei
Strong Nuclear Force
● Force that acts in the nucleus (main thing that holds nucleus together)
● Max range of 3 femtometres (x 10-15)
● Effect is same for all nucleons (doesn’t distinguish between protons and
neutrons)
● Attraction between 0.5 and 3 fm but repulsion below this (so protons and
neutrons aren’t pushed into each other)
● Either holds nucleons (protons, neutrons) together or holds quarks
● For holding nucleons together, exchange particle is pion and you call it the
‘strong nuclear force’
● For holding quarks together, exchange particle is gluon and you call it a
‘strong interaction’
Alpha 𝛼
● Contains 2 protons and 2 neutrons (same as Helium nucleus)
● +2 charge, relative mass of 4
Change in Nucleus when 𝛼 Emitted
● Nucleus loses 2 protons - atomic number goes down by 2
● Nucleus loses 2 neutrons - mass number goes down by 4
3.2.1 Particles
3.2.1.1 Constituents of the Atom
● Overall neutral charge
● Mass concentrated in nucleus
● Nucleus made from protons + neutrons (nucleons)
● Electrons exist in energy levels around nucleus
Charge (C) Mass (kg) Relative Mass Relative Charge
Proton +1.6 x 10-19 1.67 x 10-27 1 +1
Neutron 0 1.67 x 10-27 1 0
Electron -1.6 x 10-19 9.11 x 10-31 ≈ 1\2000 -1
Electrons
● DO NOT orbit nucleus like planets around a sun
● Seemingly pop in and out of existence
● Higher probability that an electron will exist in an energy level
Ions
● Charged atom
● Atom loses or gains electrons (loses = +ve charge, gains = -ve charge)
Isotopes
● Atoms of the same element (same number of protons)
● Different number of neutrons (so different mass)
Symbols
● A - mass number
● Z - atomic (proton) number
, Specific Charge
● Specific = per kg (per unit mass)
charge
● S pecif ic Charge = mass
● Measured in C kg-1 (coulombs per kg)
3.2.1.2 Stable and Unstable Nuclei
Strong Nuclear Force
● Force that acts in the nucleus (main thing that holds nucleus together)
● Max range of 3 femtometres (x 10-15)
● Effect is same for all nucleons (doesn’t distinguish between protons and
neutrons)
● Attraction between 0.5 and 3 fm but repulsion below this (so protons and
neutrons aren’t pushed into each other)
● Either holds nucleons (protons, neutrons) together or holds quarks
● For holding nucleons together, exchange particle is pion and you call it the
‘strong nuclear force’
● For holding quarks together, exchange particle is gluon and you call it a
‘strong interaction’
Alpha 𝛼
● Contains 2 protons and 2 neutrons (same as Helium nucleus)
● +2 charge, relative mass of 4
Change in Nucleus when 𝛼 Emitted
● Nucleus loses 2 protons - atomic number goes down by 2
● Nucleus loses 2 neutrons - mass number goes down by 4
