Physics: Atoms and Radiation

Question 1

what is the centre of an atom?
nucleus

the nucleus contains…
neutrons and protons

a charged atom is called an
ion

the process of adding and removing electrons from an atom is
ionisation

the nucleon number is also known as the
mass number

The mass number is equal to
protons + neutrons

atomic number is equal to
number of protons

in a neutral atom, the number of electrons is equal to
the number of protons

Bohr model of the atom
electrons in fixed energy levels circling a positive nucleus

Plum Pudding Model
negative plums embedded in a positive dough

Rutherford’s model
electrons circling a positive nucleus

alpha particle experiment was conducted by
Rutherford

nuclei are
- small
- massive
- positively charged

the majority of alpha particles went straight through the atom, showing that the atom is
mostly empty space

a light atom has ___ or fewer protons in its nucleus
20

stable atoms have an equal number of
protons and neutrons

sometimes nuclei have more energy than they require and this makes them
unstable

unstable atoms are…
radioactive

radioactive atoms can become stable by losing
energy

nuclear radiation can be _______ or _________
particles, waves

atoms lose energy by ________ ___________
emitting radiation

the process of emitting radiation is
random

radioactive atoms are often ________ of stable atoms
isotopes

what are the three main types of radiation?
alpha, beta, gamma

Isotopes have the same number of ______ but different number of _________
protons, neutrons

isotopes have the same ______ number but different _____ numbers
atomic, mass

alpha particles are
helium nuclei

What is the most ionising type of radiation?
Alpha

What is the most penetrating type of radiation?
Gamma

what is the least penetrating type of radiation?
Alpha

what happens to the nucleus in alpha decay?
loses 2 protons and 2 neutrons

what happens to the nucleus in beta decay?
neutron changes into a proton

what particles are emitted in alpha decay?
2 protons and 2 neutrons

what particles are emitted in beta decay?
an electron is created and immediately emitted

Beta radiation is _________ ionising
moderately

gamma rays are waves of ___________ radiation
electromagnetic

gamma radiation is ____________ ionising
weakly

atom before decay –>
atom(s) after decay + radiation emitted

gamma rays are a way of getting rid of _______ ______ from a nucleus
excess energy

gamma rays do not change the _____ or _____ of the nucleus
charge, mass

what is a half-life?
the average time taken for the count rate to fall by half is always the same.

the count rate after n half-lives =
the initial count rate/2 to the power of n

____________ changes into radon when it decays
uranium

radon is dangerous because
the radiation ionised cells which causes cell dagga or even cancer

what type of radiation is used for maintaining a constant thickness of metal sheet?
beta

what type of radiation is used in smoke alarms?
alpha

what type of radiation is used for detecting leaks?
gamma

alpha particle charge
2+

beta particle charge
1-

gamma particle charge
0

alpha particle deflection by magnetic or electric fields
deflected a little, opposite direction to beta

beta particle deflection by magnetic or electric fields
deflected quite a lot, opposite direction to alpha

gamma particle deflection by magnetic or electric fields
no deflection, not affected by either type of field

radiation can be detected by
- photographic film
- cloud chambers
- Geiger-Muller

what type of isotope is radon gas?
an alpha emitting isotope

nuclear fission is splitting an atom’s nucleus into
two smaller nuclei

nuclear fission releases
two or three neutrons and energy

what is a chain reaction?
A chain reaction occurs in a nuclear reactor when each fission event causes further fission events.

What do control rods do in a nuclear reactor?
They absorb neutrons to stop the chain reaction

What is nuclear fusion?
the process of combining lightweight nuclei to make heavier nuclei

Fusion reactors have the advantage of
low fuel, little radioactive waste

a fusion reactor must be at a ______ __________ temperature before nuclear fusion can take place
very high