Atoms and Nuclear Physics Flashcards
What is the radius of an atom?
1×10⁻¹⁰m.
What is the radius of the nucleus?
10,000 times smaller than the radius of the atom (1×10⁻¹⁴m).
What were atoms thought to be before the discovery of the atom?
Solid balls of mass.
What is the ‘plum pudding’ model of the atom?
A ball of positive charge with negative electrons spread throughout.
What can cause changes in distance from electrons to the nucleus?
Absorption or emission of electromagnetic radiation.
What is an isotope?
Atoms of the same element that have the same number of protons (the same atomic number) but differ in the number of neutrons.
What was the alpha particles scattering experiment?
Alpha particles fired at a thin gold foil. Particles were scattered and bounced back, indicating there was a small positive nucleus, but mostly empty space.
What is the current model of the atom called?
The Nuclear Model.
What is radioactive decay?
A random process where a nucleus gives out radiation and loses mass and becomes more stable.
What is an alpha particle?
It has the same mass as a helium nucleus: 2 protons and neutrons.
What is a beta particle?
A single, fast moving electron.
What is a gamma ray?
A high frequency, shirt wavelength electromagnetic wave.
What is the fourth type of nuclear radiation?
A neutron ejected by the nucleus.
What happens to the atomic and mass numbers in alpha decay?
The atomic number decreases by 2 and the mass number decreases by 4.
What happens to the atomic number is beta decay?
The atomic number increases by 1.
What is meant by ‘half-life’?
The time taken for the number of nuclei of the isotope in a sample to halve, or the time taken for the count rate of a sample to fall to half its initial level.
What is meant by irradiated?
When a material has been exposed to ionising radiation but does not release ionising radiation itself.
What is meant by radioactive contamination?
When a material contains an unwanted radioactive source emitting ionising radiation.
What stops alpha particles?
Thin paper.
What stops beta particles?
A few millimetres of aluminium.
What stops gamma rays?
A few centimeters of lead.
What is the range of an alpha particle?
3-5cm.
What is the range of an beta particle?
15cm.
What is the range of a gamma ray?
Very long.
