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Physics Topic 4 Atomic Structure - Coggle Diagram
Physics Topic 4 Atomic Structure
Atoms and Isotopes
Isotope
Different forms of the same element that a have the same number of protons but different number of neutrons.
Atom
same number of protons and electrons.
Ions
Unequal number of electrons and protons.
Negative Ion: Electrons gained
Positive Ion: Electrons lost
Mass Number
Number of protons and neutrons.
Atomic Number
Number of protons.
Discovery of the Nucleus
1987
J J Thomson discovered electrons and they're negatively charged.
1904
Thomson suggested the 'Plum Pudding Model' which was a spherical ball of positive charge with electrons in it.
1909
Geiger and Madsen fired alpha particles at thin gold foil. discovered some went through, some bounced off and some were deflected.
1911
Rutherford used evidence from the alpha scattering experiment to say particles were deflected because of electrostatic interaction between the nucleus. He said the nucleus was all positively charged and the electrons were outside the nucleus. The nucleus and electrons balanced each other perfectly so it was neutral.
1913
Bohr suggested the modern model of an atom- electrons orbit the nucleus in shells/ energy levels. His research also led him to finding protons.
1932
Chadwick discovered neutrons in the nucleus.
Radiation
Decay
Alpha
Ionising Power: Very strong
Penetration: Stopped by paper
Range in Air: Few cm
Beta
Range in Air: Few m
Ionising Power: medium
Penetration: Aluminium
Gamma
Range in Air: Great distances
Ionising power: weak
Penetration: Lead
Radioactive decay
unstable atoms randomly emitting radiation to become stable.
Detecting
Use Geiger Muller tube
Unit
: Becquerels (Bq)
Nuclear Fission and Fusion
Fission
One large unstable nucleus that makes two smaller nuclei. Chain reaction is formed. Used in nuclear power stations.
Fusion
Two small nuclei join together to make one big nucleus. Occurs in stars.
Fuel Rods
Made of U-238, ‘enriched’ with U-235 (3%). Long and thin to allow neutrons to escape, hitting nuclei.
Control Rods
Made of Boron. Controls the rate of reaction. Boron absorbs excess neutrons.
Concrete
Neutrons hazardous to humans – thick concreate shield protects workers.
Hazards and Uses of Radiation
Half life
the time taken to lose half of its radioactivity.
Sievert
Unit to measure dosage of radiation.
Uses
different isotopes have different half lives. A longer half life used lower doses. A shorter half life is used in bigger doses.
Tracers
Used within the body. Isotope with short half life injected, allowed to circulate and collect in damaged areas. PET scanner used to detect emitting radiation. Must be beta or gamma as alpha does not penetrate the body.
Radiation Therapy
Used to treat cancer. Cancer cells are killed by gamma rays. High dose used to kill cells. Healthy cells are protected as a gamma ray gun is used.
