atomic structure Flashcards
radius of an atom
1 x 10 - 10 metres
how does the radius of the nucleus compare to that of an atom
at least 10 000 times smaller
where is most of the mass in an atom concentrated?
the nucleus
how are electrons arranged in atoms
energy levels
what happens when an electron absorbs electromagnetic radiation
moves to a higher energy level
what happens when an electron emits electromagnetic radiation
moves to a lower energy level
what is the mass of a proton
1
what is the mass of a neutron
1
what is the mass of an electron
1/2000 (nearly 0)
what is the charge of a proton
1
what is the charge of an electron
-1
what is the charge of a neutron
0
where are protons found
in the nucleus of an atom
where are neutrons found
in the nucleus of the atom
where are electrons found
in energy levels orbiting the nucleus
what is the atomic number
the number of protons
what is the mass number
the number of protons and neutrons
how do you find the number of neutrons in an atom
mass number - atomic number
why do atoms have no overall charge
they have the same number of protons and electrons
how do ions get charged
by an atom gaining or loosing electrons
how can atoms turn into positive ions?
lose one or more outer electrons
what is an isotope?
atoms of the same element with the same number of protons but different number of neutrons
what can lead to a scientific model being replaced
new experimental evidence
before the electron was discovered atoms were thought to be…
tiny indivisible spheres
what discovery led to the plum pudding model
the electron
what was the plum pudding model?
a ball of positive charge with negative electrons embedded in it
draw the plum pudding model
google it
what were the results of the alpha scattering experiment?
most particles passed straight through, some were deflected by small angles, a few deflected by large angles
what conclusion was made from the alpha scattering experiment
the mass of an atom was concentrated in the centre (nucleus) and that the nucleus was charged
what improvements did neils bohr suggest
electrons orbit at specific distances
what was the first subatomic part of the nucleus to be discovered
the proton
what did james chadwick discover
the neutron
what is radioactive decay
unstable nuclei give out radiation as they change to become different elements that are more stable
can we predict when an atom will decay?
no, its a random process
what is activity
the rate at which a source decays
what are the units for radioactivity
becquerel (Bq)
what are the different types of radiation
alpha particle, beta particle, gamma ray, neutron
what is an alpha particle
2 neutrons 2 protons
what is a beta particle
high speed electron ejected from the nucleus as a neutron turns into a proton
how might an alpha particle be represented in a nuclear equation
4
He
2
how might a beta particle be represented in a nuclear equation
0
e
-1
what is a gamma ray
electromagnetic radiation from the nucleus
what is ionising radiation
removes electrons from atoms
which type of radiation is the most ionising
alpha
which type of radiation is the least ionising
gamma
which type of radiation is the most penetrating
gamma
which type of radiation is least penetrating
alpha
what is a half life
the time it takes for the number of nuclei of the isotope in a sample to halve
what is radioactive contamination
radioactive atoms on other materials
what is irradiation
exposing an object to nuclear radiation
what are the natural sources of background information
rocks and cosmic rays from space
what are the man made sources of background radiation
nuclear weapons testing, nuclear accidents
what are the uses of radiation in medicine
exploration of internal organs, control or destruction of unwanted tissues
what is nuclear fission
the splitting of a large and unstable nucleus
what is usually needed for nuclear fission
the unstable nucleus absorbs a neutron
