P6.1 Flashcards
what is an atomic nuclei composed of?
protons and neutrons
what is the charge on atomic nuclei?
positive
how would having atoms of the same element differ in nuclear mass?
by having a different number of neutrons
why would nuclei emit alpha/ beta particles, neutrons and/or gamma rays?
because some nuclei are unstable
describe alpha radiation
a) the structure
b) the symbol
c) how it is produced
d) the equation symbol
e) the charge
a) particle
b) α
c) 2 protons and 2 neutrons emitted from the nucleus
d) 4
He
2
e) +2 charge
in simple terms what is radioactivity?
energy emitted by a nucleus
describe beta radiation
a) the structure
b) the symbol
c) how it is produced
d) the equation symbol
e) the charge
a) particle
b) β
c) neutron turns into a prelectron emitted by nucleus
d) 0
e
-1
e) -1 charge (ITS AN ELECTRON)
do electrons orbit around the nucleus?
and if not, what do they do instead
- they do not
- they occupy discrete energy levels
where is the lowest energy level on an atom?
and what is it called
closest to the nucleus
- called ground state
do all atoms have the same values for energy levels?
no, different atoms have different values for energy levels
how can an electron be excited?
by absorbing EM radiation
what causes electrons to move up to a higher energy level (from a low energy level)
by gaining energy (ie. absorbing EM radiation)
what does it mean when an electron is excited?
inner electron rises to a higher energy level
what does it mean when an atom has been ionised?
the outer electron has absorbed enough EM radiation to leave the atom entirely
- so atom becomes a positively charged ion
what us the best way to excite electrons?
shine light on them
when can an electron absorb a photon?
and what happens when it does so
when the energy of the photon matches exactly the energy difference between two levels
- it excites to a higher energy level
if a photon’s energy is slightly above the energy difference between tht two levels, will it be absorbed by the electron?
no it will not, it must be the EXACT difference
what happens to the photon when it is absorbed?
disappears
what happens if a photon is not absorbed?
it passes straight through the atom
can a photon be partially absorbed by an electron?
no, must be absorbed ENTIRELY by a single electron
what is the energy of the photon proportional to?
proportional to the frequency of the EM radiation (and so a specific wavelength)
why do electrons return to their original energy levels?
as only a certain number of electrons are allowed to exist at any given energy level
explain what happens when electrons de-excite
- emit energy as radiation (in the form of photons)
can atoms/nuclei only generate and absorb specific frequencies?
no, radiation can be absorbed/emitted from any part of the EM spectrum
- as it depends on how much energy is needed for an electron to move to a higher energy level
when electrons de-excite, do they emit the energy all at once?
can be all at once, or a series of steps
- but total radiation emitted is equal to the radiation/energy absorbed by photon
what does an absorption spectrum show?
a set of frequencies of radiation absorbed by an atom when excited electrons move to higher energy levels
how can you use an absorption spectrum to see what an atmosphere is made of?
as the black lines show which frequencies are missing/have been absorbed
- and each atom absorbed certain frequencies/wavelengths in the EM spectrum
what does an emission spectrum show?
set of frequencies of radiation emitted by an atom when excited electrons move to lower energy levels
are the energies that electrons have in an atom positive or negative?
always negative, as they are ‘bound’ to the atom
what is a photon?
a packet of energy in which EM radiation is emitted and absorbed
why would an object emit visible light after absorbing UV radiation?
(ie. glow in the dark objects)
- as the radiation emitted by the de-exciting electrons is released in a series of steps
- which have photons of a lower energy released (and therefore frequency)
- so a different wavelength is emitted
- wheras visible light was absorbed in one go
