Define atomic number .

The atomic number (or proton number ) is the number of protons in the nucleus of an atom. It is also equal to the number of electrons in the atom.

The mass number (or nucleon number ) is the total number of protons and neutrons in the nucleus of an atom.

What are the relative charge and relative mass of a proton , a neutron and an electron ?

Proton : charge +1, mass 1. Neutron : charge 0, mass 1. Electron : charge −1, mass 1/2000 (negligible).

How can the number of neutrons in an atom be calculated?

Number of neutrons = mass number − atomic number.

An atom has no overall charge because the number of ______ is equal to the number of ______ .

An atom has no overall charge because the number of electrons is equal to the number of protons .

True or False? The nucleus of an atom contains protons and electrons.

False. The nucleus contains protons and neutrons ; electrons orbit around the nucleus.

Atoms of the same element with an equal number of protons but a different number of neutrons .

Chlorine-35 and chlorine-37 are both isotopes of chlorine, with 17 protons each. How many neutrons does each isotope have?

Chlorine-35 has 35 − 17 = 18 neutrons . Chlorine-37 has 37 − 17 = 20 neutrons .

The note names two rarer isotopes of hydrogen besides the common form. What are they, and which is rarer?

Deuterium (about 2 in every 10 000 hydrogen atoms) and tritium (about 1 in every billion billion atoms). Tritium is far rarer than deuterium.

Some isotopes are more ______ than others due to an imbalance of protons and neutrons, making them more likely to ______ .

Some isotopes are more unstable than others due to an imbalance of protons and neutrons, making them more likely to decay .

True or False? Isotopes of the same element have a different number of protons.

False. Isotopes have the same number of protons ; it is the number of neutrons that differs.

What determines which element an atom belongs to, whatever isotope it is?

The number of protons — for example, all carbon atoms have 6 protons and all iron atoms have 26 protons, regardless of neutron number.

Define radioactive decay .

The process by which an unstable nucleus emits radiation (a high-energy particle or wave) to become more stable.

Why is carbon-14 an unstable isotope of carbon?

It has two extra neutrons compared to the stable isotope carbon-12, giving it an imbalance of protons and neutrons.

What three properties are used to identify alpha, beta and gamma radiation?

Their nature (what type of particle or wave), their ionising ability , and their penetrating power .

Alpha particles have the ______ ionising ability but the ______ penetrating power of the three types of radiation.

Alpha particles have the highest ionising ability but the lowest penetrating power of the three types of radiation.

What material stops each of alpha, beta and gamma radiation?

Alpha is stopped by a thin sheet of paper . Beta is stopped by a few millimetres of aluminium . Gamma is only reduced, not fully stopped, by a few centimetres of lead .

True or False? Scientists can predict exactly when a particular unstable nucleus will decay.

False. Radioactive decay is random and spontaneous — it is not possible to predict precisely when a given nucleus will decay.

Define a gamma ray , in terms of its nature.

An electromagnetic wave emitted from an unstable nucleus; it has the highest energy of all electromagnetic waves.

In Core Practical 13 (investigating radiation), what are the independent and dependent variables?

Independent variable : the absorber material used. Dependent variable : the count rate measured.

Name three control variables in Core Practical 13.

The radioactive source used, the distance between the source and the GM tube, and the location (background radiation level).

Why is the count rate measured with no radioactive source present at the start of Core Practical 13?

To measure the background radiation , which is then subtracted from later readings so results reflect only the radiation from the source (giving the corrected count rate ).

In Core Practical 13, what does it mean if a source's count rate drops to background level once a particular absorber is in place?

All of the radiation being emitted has been absorbed by that material.

If the count rate falls when ______ is placed between the source and detector, the source is emitting alpha radiation.

If the count rate falls when paper is placed between the source and detector, the source is emitting alpha radiation.

True or False? In Core Practical 13, radioactive sources should be handled directly by hand to keep them steady.

False. Sources should be handled using tongs and pointed away from the body, and stored in a lead-lined container when not in use.

How can random errors be reduced in Core Practical 13?

Use a source with a long half-life and an activity well above background level , and repeat readings, taking averages.

What happens to the mass number and atomic number of a nucleus during gamma decay ?

Both the mass number and atomic number stay the same — only the energy of the nucleus decreases.

What happens to the mass number and atomic number of a nucleus during neutron emission ?

The mass number decreases by 1 ; the atomic number stays the same , so an isotope of the original element is formed.

In a balanced nuclear decay equation, what two quantities must be equal on both sides of the arrow?

The sum of the mass numbers and the sum of the atomic numbers must each be the same before and after the decay.

True or False? An alpha particle is identical to a helium nucleus.

True. An alpha particle consists of two protons and two neutrons , exactly like a helium nucleus.

Define background radiation .

The radiation that exists around us all the time , from both natural and artificial sources.

Define corrected count rate .

The count rate from a radioactive source with the background count rate subtracted , giving the count rate due to the source alone.

How does photographic film detect radiation, and how is this used to monitor a worker's radiation exposure?

The film becomes darker the more radiation it absorbs. Workers such as radiographers wear film badges that are checked regularly to monitor their radiation dose.

How does a Geiger-Müller tube detect radiation?

Each time it absorbs radiation it sends an electrical pulse to a counter, producing a click or a count rate — the higher the count rate, the more radiation is being absorbed.

Name three natural sources of background radiation.

Radon gas from rocks and buildings, cosmic rays from space, and radioactive material in food and drink (including carbon-14 in biological material).

A Geiger counter records 285 counts per minute with a source present and 24 counts per minute with no source present, so the corrected count rate is 285 − 24 = ______ counts per minute.

A Geiger counter records 285 counts per minute with a source present and 24 counts per minute with no source present, so the corrected count rate is 285 − 24 = 261 counts per minute.

True or False? Radon gas can be detected by taste or smell before it reaches a dangerous concentration.

False. Radon gas is tasteless, colourless and odourless ; it can only be detected using a Geiger counter .

IGCSEPhysicsEdexcelPhysics (Modular)Unit 2Flashcards8. Radioactivity & ParticlesProperties of Radiation

Properties of Radiation (Edexcel IGCSE Physics (Modular): Unit 2): Flashcards

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FrontAtomic Structure
Define atomic number.

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Cards in this collection (41)

Define atomic number.
The atomic number (or proton number) is the number of protons in the nucleus of an atom. It is also equal to the number of electrons in the atom.
Define mass number.
The mass number (or nucleon number) is the total number of protons and neutrons in the nucleus of an atom.
What are the relative charge and relative mass of a proton, a neutron and an electron?
Proton: charge +1, mass 1.
Neutron: charge 0, mass 1.
Electron: charge −1, mass 1/2000 (negligible).
How can the number of neutrons in an atom be calculated?
Number of neutrons = mass number − atomic number.
An atom has no overall charge because the number of ______ is equal to the number of ______.
An atom has no overall charge because the number of electrons is equal to the number of protons.
True or False?
The nucleus of an atom contains protons and electrons.
False.
The nucleus contains protons and neutrons; electrons orbit around the nucleus.
What is nuclear notation?
Writing an atom's element symbol together with its mass number (top) and atomic number (bottom), for example ${}_{6}^{12}C$ .
Define isotope.
Atoms of the same element with an equal number of protons but a different number of neutrons.
Chlorine-35 and chlorine-37 are both isotopes of chlorine, with 17 protons each. How many neutrons does each isotope have?
Chlorine-35 has 35 − 17 = 18 neutrons.
Chlorine-37 has 37 − 17 = 20 neutrons.
The note names two rarer isotopes of hydrogen besides the common form. What are they, and which is rarer?
Deuterium (about 2 in every 10 000 hydrogen atoms) and tritium (about 1 in every billion billion atoms). Tritium is far rarer than deuterium.
Some isotopes are more ______ than others due to an imbalance of protons and neutrons, making them more likely to ______.
Some isotopes are more unstable than others due to an imbalance of protons and neutrons, making them more likely to decay.
True or False?
Isotopes of the same element have a different number of protons.
False.
Isotopes have the same number of protons; it is the number of neutrons that differs.
What determines which element an atom belongs to, whatever isotope it is?
The number of protons — for example, all carbon atoms have 6 protons and all iron atoms have 26 protons, regardless of neutron number.
Define radioactive decay.
The process by which an unstable nucleus emits radiation (a high-energy particle or wave) to become more stable.
Why is carbon-14 an unstable isotope of carbon?
It has two extra neutrons compared to the stable isotope carbon-12, giving it an imbalance of protons and neutrons.
What three properties are used to identify alpha, beta and gamma radiation?
Their nature (what type of particle or wave), their ionising ability, and their penetrating power.
Alpha particles have the ______ ionising ability but the ______ penetrating power of the three types of radiation.
Alpha particles have the highest ionising ability but the lowest penetrating power of the three types of radiation.
What material stops each of alpha, beta and gamma radiation?
Alpha is stopped by a thin sheet of paper.
Beta is stopped by a few millimetres of aluminium.
Gamma is only reduced, not fully stopped, by a few centimetres of lead.
True or False?
Scientists can predict exactly when a particular unstable nucleus will decay.
False.
Radioactive decay is random and spontaneous — it is not possible to predict precisely when a given nucleus will decay.
Define a gamma ray, in terms of its nature.
An electromagnetic wave emitted from an unstable nucleus; it has the highest energy of all electromagnetic waves.
In Core Practical 13 (investigating radiation), what are the independent and dependent variables?
Independent variable: the absorber material used.
Dependent variable: the count rate measured.
Name three control variables in Core Practical 13.
The radioactive source used, the distance between the source and the GM tube, and the location (background radiation level).
Why is the count rate measured with no radioactive source present at the start of Core Practical 13?
To measure the background radiation, which is then subtracted from later readings so results reflect only the radiation from the source (giving the corrected count rate).
In Core Practical 13, what does it mean if a source's count rate drops to background level once a particular absorber is in place?
All of the radiation being emitted has been absorbed by that material.
If the count rate falls when ______ is placed between the source and detector, the source is emitting alpha radiation.
If the count rate falls when paper is placed between the source and detector, the source is emitting alpha radiation.
True or False?
In Core Practical 13, radioactive sources should be handled directly by hand to keep them steady.
False.
Sources should be handled using tongs and pointed away from the body, and stored in a lead-lined container when not in use.
How can random errors be reduced in Core Practical 13?
Use a source with a long half-life and an activity well above background level, and repeat readings, taking averages.
Define alpha decay, in terms of the change to mass and atomic number.
An alpha particle ( ${}_{2}^{4}α$ ) is emitted from the nucleus; the mass number decreases by 4 and the atomic number decreases by 2.
Define beta decay, in terms of the change to mass and atomic number.
A neutron changes into a proton and an electron; the electron ( ${}_{- 1}^{0}β$ ) is emitted, the mass number stays the same and the atomic number increases by 1.
What happens to the mass number and atomic number of a nucleus during gamma decay?
Both the mass number and atomic number stay the same — only the energy of the nucleus decreases.
What happens to the mass number and atomic number of a nucleus during neutron emission?
The mass number decreases by 1; the atomic number stays the same, so an isotope of the original element is formed.
In a balanced nuclear decay equation, what two quantities must be equal on both sides of the arrow?
The sum of the mass numbers and the sum of the atomic numbers must each be the same before and after the decay.
In the decay ${}_{84}^{212}P o \to_{82}^{208} P b +_{2}^{4} α$ , the equation is balanced because 212 = 208 + 4 and 84 = ______ + ______.
In the decay ${}_{84}^{212}P o \to_{82}^{208} P b +_{2}^{4} α$ , the equation is balanced because 212 = 208 + 4 and 84 = 82 + 2.
True or False?
An alpha particle is identical to a helium nucleus.
True.
An alpha particle consists of two protons and two neutrons, exactly like a helium nucleus.
Define background radiation.
The radiation that exists around us all the time, from both natural and artificial sources.
Define corrected count rate.
The count rate from a radioactive source with the background count rate subtracted, giving the count rate due to the source alone.
How does photographic film detect radiation, and how is this used to monitor a worker's radiation exposure?
The film becomes darker the more radiation it absorbs. Workers such as radiographers wear film badges that are checked regularly to monitor their radiation dose.
How does a Geiger-Müller tube detect radiation?
Each time it absorbs radiation it sends an electrical pulse to a counter, producing a click or a count rate — the higher the count rate, the more radiation is being absorbed.
Name three natural sources of background radiation.
Radon gas from rocks and buildings, cosmic rays from space, and radioactive material in food and drink (including carbon-14 in biological material).
A Geiger counter records 285 counts per minute with a source present and 24 counts per minute with no source present, so the corrected count rate is 285 − 24 = ______ counts per minute.
A Geiger counter records 285 counts per minute with a source present and 24 counts per minute with no source present, so the corrected count rate is 285 − 24 = 261 counts per minute.
True or False?
Radon gas can be detected by taste or smell before it reaches a dangerous concentration.
False.
Radon gas is tasteless, colourless and odourless; it can only be detected using a Geiger counter.

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