KO5 Atomic Structure Flashcards
State the approximate radius of a typical atom.
Approximately 0.1 nm
Describe the structure of an atom.
A central nucleus comprised of protons and neutrons surrounded by electrons.
State the fraction of the radius of an atom taken up by the radius of the nucleus.
Approximately 1/10000th the size
State where the majority of the mass of an atom is concentrated.
In the nucleus.
State the sign of the overall charge of the nucleus.
Positive
State the relative charge of a proton.
1
State the relative charge of a neutron.
0
State the relative charge of an electron.
-1
State the relative mass of a proton.
1
State the relative mass of a neutron.
1
State the relative mass of an electron.
1/1800
Describe the arrangement of electrons around the nucleus in an atom.
In energy levels (at fixed distances from the nucleus).
How can electrons move to higher energy levels?
By absorbing electromagnetic radiation.
How can electrons move to lower energy levels?
By emitting electromagnetic radiation.
State the overall charge of an atom.
0
Explain why atoms have an overall neutral charge.
The number of protons equals the number of electrons.
State what is the same about all atoms of the same element.
The number of protons
State the information provided by the atomic number of an atom.
The number of protons
State the information provided by the mass number of an atom.
The number of protons plus the number of neutrons
Define isotopes.
Atoms of the same element with different numbers of neutrons.
When an isotope of an element is formed, does the mass number or the atomic number change?
The mass number
Describe how ions form from atoms.
The atoms lose or gain electrons.
If an atom gains electrons, state the type of ion formed.
A negative ion
If an atom loses electrons, state the type of ion formed.
A positive ion
Describe what happens to scientific models when new experimental evidence is gathered.
The models get updated.
Describe the earliest model of an atom.
A tiny sphere that could not be divided.
Name the first subatomic particle to be discovered.
The electron
Describe how the model of the atom updated when the electron was discovered.
The atom was then considered to be a ball of positive charge with negatively charged electrons embedded into it.
Name the model of the atom with negatively charged electrons embedded into a positively charged sphere.
The plum pudding model
Name the model of the atom after the discovery of the nucleus.
The nuclear model
Name the experiment that discovered the nucleus of an atom.
The alpha particle scattering experiment
Describe what the alpha particle scattering experiment discovered about the nucleus.
The nucleus was small and positively charged.
Explain how the alpha particle scattering experiment proved that the nucleus was small.
Some alpha particles were scattered backwards, but only a very small number.
Explain how the alpha particle scattering experiment proved that the nucleus was positively charged.
Alpha particles were deflected and some were scattered backwards due to the repulsion.
Name the model of the atom that replaced the plum pudding model.
The nuclear model
Name the model of the atom that replaced the nuclear model.
The Bohr model
Describe the Bohr model of the atom.
The atom has a small positively charged nucleus, with electrons orbiting at specific distances (energy levels).
Name the second subatomic particle to be discovered.
The proton
Name the third subatomic particle to be discovered.
The neutron
State where within an atom nuclear radiation is emitted from.
The nucleus
Explain why unstable nuclei emit radiation.
To become more stable.
Define radioactive decay.
When an unstable nucleus emits radiation to become more stable.
Name the two things that are indicative of a material being radioactive.
It contains unstable nuclei and emits radiation.
Why is radioactive decay considered a random process?
The time in which a particular nucleus will decay cannot be predicted.
Define activity in the context of radioactive decay.
The number of decays per second.
In the context of radioactive decay, state the standard units for activity.
Becquerels (Bq)
Define count-rate in the context of radioactive decay.
The number of decays recorded per second by a detector.
Name the piece of equipment used to measure radioactive decay.
A Geiger-Muller tube
Explain why the count-rate is always less than the activity.
Not all the radiation that is emitted is detected.
Name the four types of nuclear radiation.
Alpha, beta, gamma and neutrons
State what an alpha particle is made of.
Two protons and two neutrons (a Helium nucleus)
State what a beta particle is made of.
A high speed electron
State what a gamma ray is made of.
Electromagnetic radiation (a high energy wave)
Name the three types of nuclear radiation that are ionising.
Alpha, beta and gamma
Describe how a nucleus emits beta radiation if the nucleus has no electrons in it.
A neutron in the nucleus turns into a proton, emitting an electron in the process.
List the three types of ionising radiation from most ionising to least ionising.
Alpha, beta, gamma
List the three types of ionising radiation from most penetrating to least penetrating.
Gamma, beta, alpha
State the range of alpha radiation in air.
A few centimetres
State the range of beta radiation in air.
Around a metre
State the range of gamma radiation in air.
Many kilometres
Name the type of ionising radiation that can be stopped by paper.
Alpha radiation
Name the two types of ionising radiation that can be stopped by thin aluminium.
Alpha radiation and beta radiation
State the material needed to stop gamma radiation.
Thick lead or concrete
Name the type of ionising radiation that can be stopped by skin.
Alpha radiation
State the type of radiation represented in this image.
Alpha radiation
State the type of radiation represented in this image.
Beta radiation
Describe what happens to the mass number of an element if an alpha particle is emitted.
It decreases by four.
Describe what happens to the atomic number of an element if an alpha particle is emitted.
It decreases by two.
Describe what happens to the mass number of an element if a beta particle is emitted.
It stays the same.
Describe what happens to the atomic number of an element if a beta particle is emitted.
It increases by one.
Explain why gamma ray emission does not change the mass number or atomic number.
There is no change to the nucleus.
Define half-life in terms of activity.
The time it takes for the activity of a sample to halve.
Define half-life in terms of number of unstable nuclei.
The time it takes for the number of unstable nuclei in sample to halve.
Describe what happens to the half-life of a radioactive sample over time.
Nothing, it stays constant forever.
Describe what happens to the activity of a radioactive sample over time.
It decreases.
Describe what happens to the number of unstable nuclei in a radioactive sample over time.
It decreases.
Describe what happens to the number of stable nuclei in a radioactive sample over time.
It increases.
Define radioactive contamination.
The unwanted presence of materials containing radioactive atoms on other materials.
Explain why radioactive contamination is dangerous.
The contaminating radioactive atoms will decay, leading to irradiation.
Define irradiation.
The process of exposing an object to nuclear radiation.
Explain why irradiation is dangerous.
Exposure to radiation can lead to ionisation events.
State whether irradiated objects become radioactive.
No, because their nuclei do not become unstable.
Define background radiation.
The level of radiation that is present all the time.
Name two natural sources of background radiation.
Rocks and cosmic rays from space
Name two human-made sources of background radiation.
Fallout from nuclear weapons testing and nuclear accidents
State what affects the level of background radiation.
Geographical location
Define radiation dose.
The amount of radiation that a person has been exposed to.
Give two factors that affect the level of radiation dose.
Geographical location and occupation
State whether all radioactive elements have the same half-life.
No, different radioactive elements have vastly different half-lives.
If the half-life of a radioactive element is short, explain why this might be hazardous.
Lots of decays happen in a short space of time, so lots of radiation is emitted in a short space of time.
Give two uses of nuclear radiation in medicine.
Exploration of internal organs and control/destruction of unwanted tissue
Explain why alpha radiation is not suitable for exploring internal organs.
It won’t penetrate through the body so cannot be detected.
Define nuclear fission.
The splitting of a large and unstable nucleus.
Give two examples of elements that can undergo nuclear fission.
Polonium and uranium
The diagram shows a number of nuclei and particles. Which letter shows the nucleus that is undergoing fission?
A
The diagram shows a number of nuclei and particles. Which letter shows the neutrons that are produced during nuclear fission?
B
The diagram shows a number of nuclei and particles. Which letter shows the smaller nuclei that are produced during nuclear fission?
C
Define spontaneous fission.
Nuclear fission that happens by itself.
State whether spontaneous fission is common or rare.
Rare
Describe how nuclear fission can be made to happen.
By getting an unstable nucleus to absorb a neutron.
During nuclear fission, what does a nucleus split up into?
Two smaller nuclei, two or three neutrons, and gamma rays
In the context of nuclear fission, define chain reaction.
The neutrons released by one fission may induce fission in multiple other nuclei, releasing yet more neutrons and inducing more fission.
In nuclear reactors, is the chain reaction controlled or uncontrolled?
Controlled
In nuclear weapons, is the chain reaction controlled or uncontrolled?
Uncontrolled
Define nuclear fusion.
The joining of two light nuclei to form a heavier nucleus.
The diagram shows the process of nuclear fusion. Which letter shows the two nuclei that will fuse?
A
The diagram shows the process of nuclear fusion. Which letter shows the heavier nucleus that is formed?
B
During nuclear fusion, which has more mass: the two smaller nuclei combined or the larger nucleus produced?
The two smaller nuclei combined
During nuclear fusion, some mass is lost. State what this mass is turned into.
Energy
