SP6 Radioactivity Flashcards
What is an atom?
A positively charged nucleus containing protons and neutrons with smaller, negatively charged electrons surrounding it
What defines an element?
The number of protons present in the nucleus
What is the atomic number?
The total number of protons present in the nucleus
What is the mass number?
The total number of protons and neutrons in an atom’s nucleus
What did the Greeks think matter was made up of?
Millions of tiny uncuttable pieces of the same matter
Who created the plum pudding model?
J.J Thompson
When was the plum pudding model created?
1897
Describe the plum pudding model
An atom consisted of a ‘positive’ dough with negative electrons stuck in it
Describe the experiment that lead Rutherford to discover the atom’s nucleus
- He directed a beam of alpha particles at a thin gold foil suspended in a vacuum
- Most alpha particles went straight through—> established that atoms are mostly empty space
- a small number of alpha particles were deflected—> shows the concentration of positive charges in the nucleus
- tiny number of particles shot back—> reveals that the charge and the mass was concentrated in the nucleus
What are isotopes?
Atoms of the same elements with the same amount of protons in the nucleus but different quantities of neutrons
What are ions?
Atoms which have lost or gained electrons
What type of ion does an atom become when it loses an electron
- positively charged- cation- because there are more protons than electrons
What type of ion does an atom become when it gains an electron
- negatively charged- anion- because there are more electrons than protons
When does an electron jump to a higher orbit?
When it has absorbed EM radiation
When does an electron fall to a lower orbit?
When it has emitted EM radiation
What happens when an electron changes position within its orbits?
It produces light
What is the difference between an emission and absorption spectrum?
Emission spectrum: light emitted by the electron is displayed
Absorption spectrum: light absorbed by the electron is displayed
What is ionising radiation?
Radiation that can cause an ion to form
What is background radiation?
Weak radiation that can be detected from natural/ external sources
What are some examples of background radiation?
- cosmic rays
- radiation from underground rocks
- nuclear fallout
- medical rays
What are the ways of measuring radioactivity?
- photographic film
- Geiger-muller tube
Describe how to measure radioactivity using the photographic film
- film that goes darker when it absorbs radiation
- the more radiation it absorbs, the darker it gets
- worn as badges by people who work with radiation to check the amount of exposure they’ve had
Describe how to measure radioactivity through a Geiger-Muller tube
- Each time the tube absorbs radiation, it transmits an electrical impulse
- This produces a clicking sound
- The greater the number of clicks per second, the more radiation is present
- this is called the count rate
What are the four types of radiation?
- alpha decay
- beta minus decay
- beta plus decay
- neutron emission
Describe what occurs in alpha decay
If the nucleus is unstably large, it will emit a ‘package’ of two protons and two neutrons called an alpha particle—> causes the mass number to decrease by four—> highly ionising—> weakly penetrating