PHYSICS - RADIOACTIVITY
- Created by: Chelsey`Johnson
- Created on: 06-03-16 00:50
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- radioactivity
- STRUCTURE OF AN ATOM
- protons and neutrons have same relative mass of 1
- nucleon (mass) number = number of protons and neutrons
- proton (atomic) number = number of protons
- proton charge = 1. neutron charge = 0. electron charge = -1
- ATOMS AND IONS
- number of protons determine the element
- A (mass number / nucleon number / atomic number) = total number of nucleus
- Z (proton number / atomic number) = total number of protons
- number of neutrons = A-Z
- ions - charge
- if number of electrons changes, atom = charge, and now an ion
- remove an electron, overall charge = positive so it is a POSITIVE ION
- add an electron, overall charge = negative, so it is a NEGATIVE ION
- if number of electrons changes, atom = charge, and now an ion
- number of protons determine the element
- GAMMA RAYS
- electro-magnetic waves, so have no mass or charge
- very short wave-length and highly energetic electro-magnetic radiation
- high penetrating power
- takes thick sheet of metal or concrete to reduce them by a lot
- weakly ionising
- do not directly ionise other atoms
- given off by energetic or excited nuclei
- gamma radiation does not alter nucleon and proton numbers
- not affected by electric or magnetic fields
- electro-magnetic waves, so have no mass or charge
- EFFECT OF ALPHA AND BETA DECAY ON NUCLEI
- radioactive decay occurs in unstable nuclei
- parent nucleus ejects a particle to form a daughter
- new nucleus is excited and loses energy by giving off a gamma ray
- unstable -> stable
- new nucleus is excited and loses energy by giving off a gamma ray
- ALPHA DECAY
- very large nuclei that have a surplus of neutrons
- most alpha emitters are heavy nuclei
- mass number goes down by 4 -> 4 nucleons lost
- atomic number goes down by 2 - 2 protons lost
- helium nucleus is ejected
- BETA DECAY
- smaller nuclei with a surplus of neutrons
- high speed electron is ejected
- electron comes out of nucleus, not shells
- HALF-LIFE
- the time taken for the mass / number / percen-tage / activity of radio-active nuclei to halve
- STRUCTURE OF AN ATOM
- if number of electrons changes, atom = charge, and now an ion
- remove an electron, overall charge = positive so it is a POSITIVE ION
- add an electron, overall charge = negative, so it is a NEGATIVE ION
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