Topic 6 - Radioactivity Flashcards
The current model of the atom consists of
A positive nucleus of protons and neutrons
Surrounded by shells of negative electrons
The nucleus makes up almost all the mass but is tiny in comparison to the atom
Atoms and small molecules size
1 x 10^-10
Isotopes are
Atoms of an element with the same number of protons but a different number of neutrons. This means the atomic number stays the same but the mass number changes
Proton relative mass and charge
Mass: 1
Charge: 1
Neutron relative mass and charge
Mass: 1
Charge: 0
Electron relative mass and charge
Mass: 0 or 0.0005
Charge: -1
What is a positron
The antiparticle of an electron
Positron relative mass and charge
Mass: 0 or 0.0005
Charge: 1
Atoms are always neutral because
There is the same amount of protons and electrons
Electrons change orbit/shell when
It absorbs or emits EM radiation
If an electron absorbs EM it
Gets excited to higher shells which are higher energy levels. Then it quickly falls back.
When an electron falls back after being excited it
Emits the same amount of EM and energy as it originally absorbed
Atoms become positive ions when
They lose an electron
When an isotope nucleus is unstable it
Decays and gives out radiation. They emit one or more of alpha, beta and gamma. They can also emit neutrons
Beta particles can be
Beta-minus particles: fast moving electrons released by the nucleus
Beta-plus particles: fast moving positrons
