Atomic Model and Radioactivity Flashcards
Most alpha particles went straight through the foil
Atoms are mostly empty space
Few were deflected at large angles or straight back
The nucleus is v. dense, small and contains all the positive matter
Mass number
no. of protons plus neutrons
Atomic number
no. of protons
What is the notation of atomic no. and mass no.
The mass number is top ( A )
The atomic number is bottom ( Z )
What is mass number shortened to
A
What is atomic number shortened to
Z
Define an isotope
atoms with a different number of neutrons but the same number of protons
What is emitted in alpha decay
helium nuclei/alpha particle
What is the effect on A and Z in alpha decay
A decreases by 4, Z decreases by 2 and a new element created to balance
Describe alpha decay
2 neutrons and 2 protons are emitted from the nucleus
What is emitted in beta decay
high energy electron
describe beta decay
a neutron in the nucleus decays into a proton so a high energy electron is emitted
charge of alpha radiation
+2
Charge of beta radiation
-1
Charge of gamma radiation
no charge
Effect on A and Z in beta decay
A stays the same, Z increases by 1 and a new element to balance
What is emitted in gamma radiation
High energy EM radiation
Description of gamma radiation
Nucleus changes shape into a more stable shape, gamma radiation emitted as a result
Effect on A and Z in gamma
No change
What stops alpha
Skin or Paper
What stops beta
Thin lead or aluminium (3mm)
What reduces gamma
Thick lead or concrete
Range of alpha in air
5cm
Range of beta in air
1m
Range of gamma in air
unlimited
What is gamma used for
to kill bacteria, mould and insects on food and hospital equipment
Leak detection
medical tracers
Radiotherapy
what is nuclear fission
a neutron is absorbed into a nucleus causes the nucleus to become violently unstable.
The entire nucleus splits into two large fragments called ‘daughter nuclei’. In addition to the ‘daughter’ products, two or three neutrons also explode out and these can collide with other uranium nuclei
Causing a chain reaction
what must first occur before fission
induced fission must occur
What is induced fission
nucleus absorbing a neutron
Where does nuclear fission take place
in a nuclear reactor
What is nuclear fusion
smaller nuclei fuse to form large nucleus, needs lots of energy so only happens in stars
Where does nuclear fusion occur
only in stars
What is the lowest energy level called
ground state
What is the higher energy level called
Excited state
What is the highest energy level called
ionisation level
electron falls from high to low energy level
EM radiation is released
Electron jumps from low to high
energy is absorbed by EM radiation
what does quantised energy levels mean
it means electrons cant stay between energy levels
What must be exact to jump to a higher energy level
the amount of energy
How is beta deflected in an electric field
it is deflected towards positive as it has a NEGATIVE charge
How is alpha deflected in an electric field
it is deflected towards negative as it has positive but less as it has more mass
How is gamma deflected in an electric field
it isn’t deflected at all as it has no charge
