Particles and Radiation Flashcards
what is a particle?
a minute portion of matter
what are atoms made up of?
protons, neutrons and electrons
what is the charge of a proton?
+1
what is the charge of a neutron?
0
what is the charge of an electron?
-1
what is the proton number?
the number of protons in the nucleus
what is the proton number also called?
the atomic number
will two elements ever have the same amount of protons?
no, because it is the proton number that defines the element
how many electrons does a neutral atom have?
the same amount as it does have protons
what is the total number of protons and neutrons called?
the nucleon number
what is the nucleon number also referred to as?
the mass number
what is something called if it has the same amount of protons but a different number of neutrons?
an isotope
changing the number of neutrons…
…doesn’t affect the atom’s chemical properties
what do the number of neutrons affect?
the stability of the nucleus
in general, the greater number of neutrons compared with the protons,…
…the more unstable the nucleus is
unstable nuclei may be radioactive…
…and decay to make themselves stable
what is the relative mass of a proton?
1
what is the relative mass of an electron?
0.0005
what is the relative mass of a neutron?
1
define proton number
no. of protons in the nucleus
define nucleon number
total no. of protons & neutrons in the nucleus
what does the strong nuclear force do?
binds nucleons together
to hold the nucleus together, the strong nuclear force…
is an attractive force that is stronger than the electrostatic force
what is the range of the strong nuclear force?
very short
the strong nuclear force can only hold nucleons together if…
they are only a few femtometres apart
what happens to the strength of the strong nuclear force at about 3 femtometres?
it falls rapidly towards zero
the size of the strong nuclear force varies with…
…nucleon separation
the electrostatic repulsive force extends over a much…
…larger range (indefinately)
when is the strong nuclear force repulsive?
when it has nucleons of less than 0.5 femtometres
when does alpha emission happen?
in very BIG atoms (with more than 82 protons)
why are these atoms unstable?
because the nuclei in the atoms are too BIG for strong nuclear force
what happens when an alpha particle is emitted?
the proton number decrease by 2 and the nucleon number decreases by 4
where does beta emission happen?
in neutron-rich nuclei (isotopes)
what is beta emission?
the emission of an electron from the nucleus as well as an antineutrino
what happens to one of the neutrons in beta emission?
it changes into a proton
what happens when a beta particle is emitted?
the proton number increases by 1 and the nucleon number stays the same
what does an antineutrino carry?
energy and momentum
what tiny neutral particle is emitted in beta decay?
an antineutrino
what evidence suggests the existence of the strong nuclear force?
the electrostatic force is much larger than the gravitational force so in order to hold the nucleus together there must be another force: the strong nuclear force
why must the strong nuclear force be repulsive at short distances?
because otherwise there would be nothing stopping it crushing a nucleus to point
how does the strong interaction limit the size of a stable nucleus?
after very short space of time the strong nuclear force is larger than electrostatic and protons in nucleus are forced apart. (nucleus much bigger than this = unstable)
