Atomic Structure Flashcards
Describe:
Plum Pudding Model
1904
J.J Thomson
Spheres of negative charge with embedded electrons
Describe:
Alpha Scattering Experiment
1909
John Dalton
Beam of alpha particle fired at thin sheet of gold. Most particles went straight through but some were reflected.
Realised atom had mass concentrated at centre in positive nucleus while most of atom was empty space
Describe:
Nuclear Model
Neils Bohr
Electrons orbit nucleus at certain distances
James Chadwick 1932 - Neutron
Define:
Isotopes
Forms of an element with the same number of protons but a different number of neutrons
Same atomic number, different atomic mass
Describe:
Alpha Particles
α
Helium Nuclei
Two Neutrons
Two Protons
Short travel distance - a few cm in air
Weak Penetration - stopped by a sheet of paper
Highly Ionising
Describe:
Beta Particles
β
High-speed electron
-1 Charge
Moderate range - a few metres in air
Moderate Penetration - Stopped by aluminium
Moderately Ionising
Describe:
Gamma Rays
Ɣ
Waves of electromagnetic radiation
Long range
Moderately penetrating - Stopped by thick lead or metres of concrete
Weakly ionising
Define:
Half Life
The time taken for the number of unstable nuclei to halve
or
The time taken for the activity of a radioactive substance to halve
List:
Sources of Background Radiation
Rocks
Cosmic Rays
Nuclear Fallout
Hospitals
Define:
Irradiation
Exposure to radiation
Define:
Contamination
When unwanted radioactive atoms get onto or into an object and emit radiation
Define:
Nuclear Fission
A large unstable nucleus splitting to release two smaller, more-stable nuclei
Define:
Nuclear Fusion
Two small nuclear join to create a large heavier nucleus
