p6.1 Flashcards
whats inside the nucleus of an atom
protons and neutrons these are subatomic particles
why do the same atoms have different nuclei masses
because there is a difference in nuetrons
how is heavy water created
by adding a neutron to a hydrogen atom
what does it mean to be a ‘stable’ atom
it won’t break down or decay
what happens to an unstable atom
they emit radiation, this can be a wave or particles. when an object is made up of unstable atoms it is radioactive
whats the radiation no one cares about
neutron radiation, it emits neutrons
what are the three types of radiation and what do they emit
radiation l type l what does it emit l
alpha l particle l helium nucleus
beta l particle l a single electron
gamma l wave l a wave on the electromagnetic spectrum
how can you detect radiation
Geigur counter. this device clicks when there is radiation present, this is because the radioactive particle within the gas chamber causes a tiny electrical current
what is penetrating power, how does it differ with the different types of radiation.
penetrating power is shown by what materials the radiation can pass though
- alpha stopped by skin or paper
- beta can pass through paper but is stopped by aluminium
- gamma only stopped by lead but some may still get through
what is ionising radiation
radiation removes electrons from surrounding atoms and turns them into positively charged ions
how is ionising radiation linked to penetration power
the higher the ionising radiation the lower the penetrating power.
alpha has a high ionising power so cant travel far
gamma doesn’t ionise at all travels the farthest
what happens in alpha decay
atoms with large unstable nuclei have many protons and neutrons. two neutrons can join with two protons. this is then emitted. you can write the equation the same way you would a chemical equation. mass and charge is conserved
what happens in beta decay
a neutron decays into a proton and electron. this electron is emitted. the mass of the atom does not change. a neutron and electron is lost it gains a proton
what happens in gamma decay
the unstable element does not actually change in mass. but the unstable atom releases high frequency electromagnetic waves
what happens in neutron emission
this is when a neutron is lost. it occurs in helium - 5 (the five represents the mass number).
it loses one neutron and becomes more stable
how do you measure the activity of a radioactive substance
number of particles emitted a second is called activity / count rate. and it is measured in becquerels (Bq)
what is half life
this is the time it takes for half of the object to decay.
how are electron arranged in an atom
scientists worked out that atoms occupy different energy levels around the nucleus. electrons attempt to occupy the lowest energy level closest to the nucleus
what are photons
they are little packets of energy, the energy of a photon is proportional to its frequency
what does it mean to ‘excite’ an electron, why does it happen
this is when the electron has enough energy to jump up to the next energy level (shell). this happens when the atom absorbs the right frequency of photons
why do atoms only absorb specific frequencies
because a specific amount of energy is required to cause an electron to move to one shell to another. the energy required depends on the distance between the shells.
what is the absorption spectrum
these are the frequencies of light that are absorbed by the atom and electrons this is what causes electrons to become ‘excited’
what is the emission spectrum
this is the frequency that the atoms emit to stop the electrons being excited.
how are the emission spectrum and absorption spectrum related
the frequencies absorbed are the same as the frequencies emitted.
whats the difference between an excited atom and an ionised atom
excited - the electrons have changed energy levels
ionised - the electrons have completely left the atom
