Physics Notes – Radioactivity
Atoms are made up of protons, neutrons and electrons
Particle Relative mass Relative charge
proton 1 +1
neutron 1 0 (neutral)
, electron 1/2000 or 0.05 -1
Atomic number and mass number
Atomic number
the number of protons in its nucleus, the atomic number of each element is unique.
Mass number (atomic mass)
the total number of protons and neutrons in the atom.
Isotopes
Isotopes are atoms of an element that have the same number of protons, but different numbers of
neutrons in their nuclei.
They will react in the same way as they still have the same electron configuration. e.g., Three isotopes of
hydrogen
All hydrogen atoms contain one proton (and one electron), but they can contain different numbers of
neutrons. Hydrogen-1 is the most abundant isotope of hydrogen.
The stability of Isotopes
Protons are held in the nucleus by nuclear force (very strong over a very small distance)
Strong enough to hold nucleus together against electrostatic forces repelling protons from each other
The number of neutrons affects the balance between nuclear force and the electrostatic force
Ionising radiation
Causes atoms to lose or gain charge, forming ions
When radiation collides with neutral atoms or
molecules it alters their structure by knocking off
electrons. This will leave behind ions
Emitted from the unstable nuclei of radioactive
atoms
There are three main types: alpha, beta and
gamma radiation.
Atoms are made up of protons, neutrons and electrons
Particle Relative mass Relative charge
proton 1 +1
neutron 1 0 (neutral)
, electron 1/2000 or 0.05 -1
Atomic number and mass number
Atomic number
the number of protons in its nucleus, the atomic number of each element is unique.
Mass number (atomic mass)
the total number of protons and neutrons in the atom.
Isotopes
Isotopes are atoms of an element that have the same number of protons, but different numbers of
neutrons in their nuclei.
They will react in the same way as they still have the same electron configuration. e.g., Three isotopes of
hydrogen
All hydrogen atoms contain one proton (and one electron), but they can contain different numbers of
neutrons. Hydrogen-1 is the most abundant isotope of hydrogen.
The stability of Isotopes
Protons are held in the nucleus by nuclear force (very strong over a very small distance)
Strong enough to hold nucleus together against electrostatic forces repelling protons from each other
The number of neutrons affects the balance between nuclear force and the electrostatic force
Ionising radiation
Causes atoms to lose or gain charge, forming ions
When radiation collides with neutral atoms or
molecules it alters their structure by knocking off
electrons. This will leave behind ions
Emitted from the unstable nuclei of radioactive
atoms
There are three main types: alpha, beta and
gamma radiation.
