P4/Atomic Structure Flashcards
what is the radius of an atom?
1x10-10 m
which two particles make up the nucleus of an atom?
protons and neutrons
where, in an atom, are the electrons found?
orbiting the nucleus
the radius of the nucleus is what fraction of the radius of the atom?
1/10,000
what do we call the different distances that the electrons can be from the nucleus?
energy nucleus
how can an electron move to a higher energy level?
when the atom absorbs electromagnetic radiation
which number tells us the number of protons?
the atomic number
how can you work out the number of neutrons in an atom?
mass number-atomic number
what do we call atoms of the same element that have different numbers of neutrons?
isotopes
what do atoms turn into if they lose one or more of their outer electrons?
positive ions
before the discovery of the electron, atoms were thought to be what?
tiny spheres that could not be divided into anything smaller
the discovery of the electron led to which model of the atom?
the plum pudding model
the plum pudding model suggested that the atom is a ball of positive charge with negative electrons located where?
embedded everywhere in it
the results from the alpha particle scattering experiment led to the conclusion that the mass of an atom was concentrated at the centre (nucleus) and that the nucleus was what?
positively charged
the nuclear model replaced what?
the plum pudding model
Niels Bohr adapted the nuclear model by suggesting that electrons orbit the nucleus in what?
shells
later experiments led to the idea of which particle?
the positively charged proton
the experimental work of James Chadwick provided the evidence to show the existence of which particles within the nucleus?
neutrons
what do we call the process when an unstable nucleus gives out radiation to become a more stable nucleus?
radioactive decay
what do we call the rate at which a source of unstable nuclei decay?
activity
what is the unit for activity?
becquerel (Bq)
what do we call the number of decay that are detected each second?
count-rate
what is an alpha particle made of?
2 protons and 2 neutrons
what is a beta particle?
a high speed electron
what happens in the nucleus to make a beta particle?
a neutron turns into a proton
what is gamma radiation?
electromagnetic radiation from the nucleus
what can stop alpha particles?
a sheet of paper, a few cm of air or skin
what would you need to stop gamma radiation?
a few cm of lead or a few metres of concrete
which type of radiation is the most ionising?
alpha
which type of radiation is the least ionising?
gamma
what name is given to the amount of time it takes for half of a radioactive sample to decay?
half-life
what do we call the presence of unwanted radioactive atoms on or in other materials?
contamination
what do we call the exposure of objects to radioactivity?
irradiation
what do we call the radiation that is around us all the time?
background radiation
what units do we measure radiation dose in?
seiverts (Sv) or millisieverts (mSv)
give two ways in which radioactivity is used in medicine?
exploration of internal organs
control and destruction of cancerous tissue
what name is given to the splitting of a large nucleus in to two smaller nuclei?
nuclear fission
what particle must be absorbed by a nuclei to undergo fission?
neutron
which particles are produced during nuclear fission?
2 or 3 more neutrons
what else is released in nuclear fission?
energy
what is the danger of the extra neutrons?
a chain reaction
what is the name given to the joining together of small nuclei to make larger ones?
nuclear fusion
during nuclear fusion mass is converted into what?
energy
