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what is an ion?
a charged atom due an electron being lost or gained during ionisation, resulting in proton and electron number being different
what is ionisation?
the process of removing or adding electrons to an uncharged atom to turn it into an ion
how do you get an ion of a positive charge?
remove an electron
how do you get an ion of negative charge?
add an electron
how does radioactive particles (alpha, gamma, beta) make ions?
when they pass through a substance they collide with the atoms of the substance, either;
causing the atoms to absorb one of their electrons through the force of collision (creating a negatively charged ion)
knocking an electron out of the atom’s shell (creating a positively charged ion)
how do radioactive particles create a positively charged ion?
radioactive particles entering a substance collide with the atom’s of the substance, knocking their electrons out and creating a positively charged ion (as the substance loses their negatively charged electrons and therefore has a positive charge)
how do radioactive particles create a negatively charged ion?
radioactive particles entering a substance collide with the atom’s of the substance, making the atoms absorb one of their electrons through force of collision, and creating a negatively charged ion (as the substance now has more negatively charged electrons and therefore a negative charge)
how do non-radioactive electrons create ions?
when passing through fluorescent tubes, they collide with the atoms of the gas or vapour in the tube
which particle creates ions by passing through a fluorescent tube?
non-radioactive electrons
which particle creates ions when passing through substances?
radioactive particles (alpha, beta, gamma)
how do we measure the energy needed to ionise a gas atom (ionisation energy)?
by making electrons collide at increasing speeds with gas atoms in a sealed tube
what can we measure by making electrons collide at increasing speeds with gas atoms in a sealed tube?
the energy needed to ionise a gas atom (ionisation energy)
what is ionisation energy?
the energy needed to ionise an atom of a substance
apparatus to measure ionisation energy of gas atoms
DIAGRAM HERE
what is in the apparatus used to measure ionisation energy of gas atoms?
DIAGRAM HERE
anode (at other end of the tube from filament)
gases at low pressure inside sealed tube
heated filament emitting electrons
potential difference between anode and filament
ammeter
battery
voltmeter
resistor
what is the point of the ammeter in an ionisation energy measuring apparatus?
to measure an increase current near the anode, proving ionisation has occurred
what is the point of the voltmeter in an ionisation energy measuring apparatus?
to measure the change in potential difference applied between the anode and filament
why is the gas in an ionisation energy measuring apparatus at low pressure?
so there are less atoms within the tube, as otherwise the electrons would not be able to reach the anode
what is the point of the sliding resistor in an ionisation energy measuring apparatus?
to change voltage?
what is the purpose of the anode in an ionisation energy measuring apparatus?
to attract the electrons emitted from the heated filament
what is the purpose of the heated filament in an ionisation energy measuring apparatus?
to emit electrons that can be attracted to the positively charged anode on the other side of the tube, ionising the gas vapours when passing through the tube
measuring ionisation of gas atoms
electrons emitted from heated filament
electrons attracted to anode (positively charged metal plate) at the other end of the tube
pd between anode and filament increased to increase speed of electrons
ammeter records small current BEFORE ionisation speed reached
speed increases to the ionisation speed
at the ionisation speed, electrons have enough Ek to knock electrons out of the gas atom’s shells
why is the potential difference between the anode and filament increased?
to increase the speed of the electrons
how is the potential difference between the anode and filament increased?
using the sliding resister? which direction makes voltage bigger and smaller?
why is a small current recorded before ionisation energy is reached?
because some electrons have reached the anode
why is a large current recorded after ionisation energy is reached?
because the electrons from the heated filament have ionised the gas atoms by knocking out their electrons, there are now more electrons being attracted to the anode, meaning a greater current is recorded
in an ionisation energy measuring experiment, how do you know you have reached ionisation energy? why?
when a large current is recorded - because that means the gas atoms have had their electrons knocked out of their shells during ionisation, meaning there are more electrons being attracted to the anode, therefore a large current is recorded
what is the current like before ionisation energy is reached?
a small current, because not many electrons have reached the anode
what is the current like after ionisation energy is reached?
a large current, because electrons have been knocked from the gas atoms during ionisation, meaning there are more electrons in the sealed tube being attracted to the FUCKING anode thereFUCKINGfore there is a greater FUCKING current! FUCK !
when is the current in a ionisation energy measuring apparatus;
small?
large?
small current before ionisation energy is reached
large current after ionisation energy is reached
how do we get the ionisation energy?
by increasing the speed of the electrons until they reach ionisation speed, in which the Ek of the electrons is large enough to knock the electrons out of the gas atoms’ shells (ionising them) upon impact
at what speed of the filament electrons is ionisation energy reached?
ionisation speed
what kind of ionisation do the gas atoms in an ionisation energy measuring experiment undergo?
having their electrons knocked out of their shells by colliding filament electrons, making the atoms into positively charged ions as they lose an electron
what component of a ionising energy measuring experiment can be ignored? why?
the charge of the current, because it involves both negative (from the electrons) and positive (from the gas ions) charge, and is not relevant to what we are investigating which is ionisation energy
which place does ionisation occurring cause the largest increase in current?
near the anode, as the electrons in that area are attracted to the anode and therefore current increases
ionisation energy = ?
ionisation energy = work done on an electron = e x v = an electron volt
e = electron charge, WHAT IS IT
v = potential difference of tube
what is the work done on the (filament) electrons?
the thermal energy from the filament wire being transferred to the Ek of the emitted electrons
why is the ionisation energy the same as the work done on the filament electrons?
the work done from the transfer of thermal energy from the heated filament wire is the Ek of the emitted electrons. this means when the emitted electrons collide and successfully ionise a gas atom, the Ek of the electron is the same as the energy needed to ionise the atom. therefore work done on electron = ionisation energy
why is ionisation energy the same as an electron-volt?
ionisation energy = ev
electron-volt = eV
ionisation energy = electron volt
what is an electron-volt (eV)?
unit of energy
the work done when an electron is moved through a potential difference of 1v
what is an eV the work done of?
the work done when an electron is moved through a potential difference of 1v
work done = ?
work done = qV
q = charge
v = pd
1 eV in joules
1eV = 1.6 × 10-19 J
eV → joules
multiply by 1.6 × 10-19 J
joules → eV
divide by 1.6 × 10-19 J
what is excitation?
atoms absorbing energy from colliding electrons without being ionised. the energy moves an electron in a lower energy level to a higher energy level (i.e., an innermost shell to an outer one)
DIAGRAM
what are excitation energies?
the multiple energy values at which gas atoms absorb energy from colliding electrons and excite
are there one or multiple ionisation energies?
one, since there is one energy level that provides the electron with enough energy to overcome the electrostatic forces and be emitted from the atom
are there one or multiple excitation energies?
multiple, as electrons in different energy levels (i.e., different shells) have different energies that excite them
how do we excite atoms using gas-filled tubes?
by placing a metal grid between the filament and anode what the fuck does that do
how do we determine excitation energy in gas-filled tubes?
measuring the potential difference across the tube, since eV (electron charge x potential difference across tube) tells us the excitation energy
noting where current falls, as current falls when excitation occurs
why does a drop in current tell us the excitation energies in gas-filled tubes?
excited atoms have electrons moving up energy levels yet staying within the atom, however the colliding atom loses all Ek during excitation. this means no atomic atoms are emitted contribute to electron flow, and the existing flowing electrons (colliding electrons) stop flowing when their Ek is absorbed. therefore less electrons are flowing, so current decreases
why does excitation require energy?
because the electron that absorbs energy from a colliding source of energy (i.e., an electron) moves to a shell of a higher energy level (one that is further from the nucleus)
what does the energy from a colliding energy source (i.e., electron) need to overcome?
the energy keeping the atomic electron in an innermost shell of lower energy level in order to move it up an energy level
which is higher, ionisation or excitation energy?
excitation energy < ionisation energy
why is ionisation energy always higher than ionisation energy?
because in ionisation, enough energy is provided to completely emit the electron from the nucleus, whereas in excitation enough energy is provided to only move the electron to a shell of a higher energy level
what happens to the colliding electron during excitation?
it loses all it’s Ek , as it is absorbed by the atomic electron to move up an energy level
during excitation, where does the energy required to move an atomic electron to a shell of higher energy level come from?
it is absorbed from the Ek of the colliding electron
what happens to the current during excitation? why?
it decreases - as current is due to flow of electrons, when a colliding electron excites an atomic electron it loses all it’s Ek, therefore it is not flowing, the less electrons flow, the smaller the current, therefore during excitation, current decreases
why do ionised atoms increase current but excited atoms decrease current?
ionised atoms emit electrons which are then attracted to the anode, increasing current as more electrons are flowing
excited atoms have electrons moving up energy levels yet staying within the atom, however the colliding atom loses all Ek during excitation. this means no atomic atoms are emitted contribute to electron flow, and the existing flowing electrons (colliding electrons) stop flowing when their Ek is absorbed. therefore less electrons are flowing, so current decreases
what happens when colliding electrons lack the energy required to excite atoms?
it is deflected by the atom with no overall loss of Ek
does the Ek of a colliding atom change when it is deflected by an atom for not having sufficient enery to excite?
no, it’s Ek stays the same
