Revision Checklist for P4 Structure of the Atom Flashcards
What is the radius of an atom?
Approximately 1 × 10^-10 metres.
What is the size of the nucleus compared to the atom?
The nucleus is 1/10,000 smaller, about 1 × 10^-14 metres across.
Where is most of the mass of an atom concentrated?
In the nucleus.
How are electrons arranged in an atom?
At different distances from the nucleus at different energy levels.
What happens to electron arrangements when electromagnetic radiation is absorbed?
Electrons move further from the nucleus to a higher energy level.
What happens to electron arrangements when electromagnetic radiation is emitted?
Electrons move closer to the nucleus to a lower energy level.
What is the definition of atomic number?
The number of protons in an atom.
What is the mass number?
The total number of protons and neutrons in an atom.
In a neutral atom, how do the number of electrons compare to the number of protons?
They are equal.
How do you calculate the number of neutrons in an atom?
Mass number - atomic number.
What is an isotope?
Atoms of the same element with different numbers of neutrons.
How are ions produced?
By gaining or losing electrons.
What is the plum pudding model?
A model proposed by JJ Thomson describing atoms as a positive ‘pudding’ with negative electrons embedded.
What were the main observations from the Rutherford alpha scattering experiment?
- Most alpha particles passed through 2. Some deflected at large angles 3. A few bounced back.
What is Rutherford’s initial nuclear model?
A model proposing that atoms have a dense nucleus surrounded by electrons.
What does Bohr’s model of the atom describe?
Electrons orbiting the nucleus at fixed energy levels.
What is the significance of Chadwick’s discovery of the neutron?
It explained the missing mass in atomic nuclei and led to a better understanding of atomic structure.
Define radioactive.
The process by which unstable atomic nuclei lose energy by emitting radiation.
What is activity in the context of nuclear physics?
The rate at which a sample of radioactive material decays.
What is the count rate?
The number of decays detected per unit time.
What unit is used to measure radioactive decay?
The Becquerel (Bq).
Identify the properties of alpha particles.
- Relative mass: 4 * Relative charge: +2 * Range in air: a few cm * Penetrability: low * Ionising power: high.
Identify the properties of beta particles.
- Relative mass: 1/2000 * Relative charge: -1 * Range in air: several meters * Penetrability: moderate * Ionising power: moderate.
Identify the properties of gamma rays.
- Relative mass: 0 * Relative charge: 0 * Range in air: unlimited * Penetrability: high * Ionising power: low.
What is alpha decay?
A type of radioactive decay where an alpha particle is emitted from the nucleus.
What is beta decay?
A type of radioactive decay where a beta particle is emitted from the nucleus.
What happens during gamma radiation emission?
There is no change of element; energy is released without altering the nucleus.
What is half-life?
The time taken for half of the radioactive nuclei in a sample to decay.
How can half-life be determined?
From data or graphs showing radioactive decay.
What are the negative effects of extended irradiation on body tissue?
Damage to cells and increased risk of cancer.
What are natural sources of background radiation?
- Rocks * Cosmic rays from space.
What are man-made sources of background radiation?
- Fallout from nuclear weapons testing * Nuclear accidents.
How is radiation dose measured?
In Sieverts (Sv).
How is nuclear radiation used in medicine?
- Exploration of internal organs * Control or destruction of unwanted tissue.
What is nuclear fission?
The splitting of a heavy nucleus into lighter nuclei, releasing energy.
What is induced nuclear fission?
Fission initiated by the absorption of a neutron.
What is a chain reaction in nuclear fission?
A series of reactions where the products of one fission event cause further fission events.
What distinguishes controlled fission from uncontrolled fission?
Controlled fission occurs in a reactor, while uncontrolled fission occurs in a bomb.
What is nuclear fusion?
The process of joining two light nuclei to form a heavier nucleus, releasing energy.
What fuels the sun?
Nuclear fusion.
