Physics Flashcards
Most of the mass of an atom is contained within a small dense ____. The nucleus is made of _____ and _____
nucleus
protons
neutrons
Protons have a _____ charge and _____ have zero charge. Electrons ____ around the nucleus.
positive
neutrons
orbit
Electrons have a negative charge and a small ____
mass
The atomic number of an element tells us how many _____ are in the nucleus. The element will also have the same number of ______
protons
electrons
The atomic mass of the electrons tells us how many protons and _____ there are in the ______
neutrons
nucleus
To calculate the number of neutrons, we subtract the atomic ______ from the atomic _____
number
mass
What makes hydrogen unique when compared to other elements?
No neutrons
Isotope
Has the same number of protons and electrons but a different number of neutrons
What is the atomic structure of a ‘normal’ hydrogen
One proton in nucleus and one electrons orbiting the nucleus
What is the difference between an ion and an atom
An ion is a charged atom
If an atom gains one electron, what would it’s overall charge be?
-1
If an atoms loses one electron, what would it’s overall charge be?
+1
Alpha radiation; 1) description 2) electric charge 3 )relative atomic mass 4) penetrating power 5) ionizing effect 6) effect of magnetic/electric field
1) 2 neutrons, 2 protons. An alpha particle is the same s a helium nucleus
2) +2
3) 4
4) stopped by paper or a few cm of air
5) strongly ionizing
6) weakly deflected
Beta radiation;
1) description
2) electric charge
3) relative atomic mass
4) penetrating power
5) ionizing effect
6) effect of magnetic/electric field
1) high energy electron
2) -1
3) 1/2000
4) stopped by a few mm of aluminium
5) weakly ionizing
6) strongly deflected
Positron (beta plus) radiation;
1) description
2) electric charge
3) relative atomic mass
4) penetrating power
1) high energy and high speed particle/ positive electron/ antimatter
2) +1
3) 1/2000
4) annihilates immediately
Gamma radiation;
1) description
2) electric charge
3) relative atomic mass
4) penetrating power
5) ionizing effect
6) effect of magnetic/electric field
1) high energy electromagnetic radiation
2) 0
3) 0
4) stopped by several cm of lead or several m of concrete
5) very weakly ionizing
6) not deflected
What happens to cause an atom to emit energy?
an electron moves to a higher orbit (energy level)
What happens when an atoms absorbs energy?
An electron moves to a lower orbit
What happens when an atom becomes an ion?
The electron completely leaves the orbits
The first person to suggest the idea of atoms was the Greek philosopher _______. This idea is a substance is called an element.
Democritus 4500BC
The idea that the atomic structure have changed over time. _____ reintroduced the idea that everything is made of atoms. He said atoms were solid of spheres of matter that could not be split.
John Dalton, 1803
The discovery of radioactivity. In a radioactive atom, the nucleus is unstable and so it emits particles or waves of radiation to form a more stable atom.
Henri Becquerel, 1896
The discovery of tiny particles with a negative charge. Also discovered the existence of electrons. It didn’t fit with Dalton’s model so created a new one. - PLUM PUDDING MODEL
J.J Thomson, 1897
Came up with his ‘nuclear’ model of the atom. He made many important discoveries about radioactivity and atomic structure.
Ernest Rutherford, 1911
Half life
The time it takes the number of radioactive nuclei in a sample to decrease by 50%
Geiger and Marsden’s gold foil experiment
A thin sheet of gold foil was placed in front of a lead box containing alpha radiation.
What happened in the gold foil experiment?
1) most alpha particles went straight through the gold foil, without any deflection
2) some alpha particles were slightly deflected by the gold foil
3) a few alpha particles were bounced back from the gold foil
What were the results of the gold foil experiment?
- Most of the atom is empty space
- It has positive charge and most of its mass is in a tiny central nucleus
- Electrons orbit the nucleus at a distance, like planets around the sun
What does fluorescent mean? Explain what happens to make a fluorescent material appear really bright?
A fluorescent material absorbs some electromagnetic energy and then emits it straight away. The emitted energy usually has a longer wavelength than the absorbed energy; UV is absorbed and re-emitted as visible light.
Explain the difference between a ‘fluorescent’ material and a ‘phosphorescent’ material.
A phosphorescent material emits the electromagnetic energy it has absorbed much later after doing so however fluorescent materials emits the energy straight away
Background radiation
Natural sources of radiation (and artificial sources)
Why are plants radioactive?
They take in carbon-14 from the atmosphere
Why do we increase our own radiation levels by eating meat?
The cows eat the radioactive grass with the carbon-14 in it as well as breathing it in on a daily basis. This will keep happening until they die which is when they are used to sell, cook and eat their meat.
Why is a wooden table or shelf radioactive?
The wood was once a living tree breathing in the carbon-14 during photosynthesis
2 examples of medical sources of background radiation?
X-rays and CT scanner
What are cosmic rays? What objects in space do they come from?
A highly energetic atomic nucleus or other particle travelling through space at a speed approaching that of light
What is radon gas? Where does it come from? Why is it dangerous to humans?
Radon is a naturally-occurring radioactive gas that can cause lung cancer. Radon gas is inert, colourless and odourless. Radon is natural in the atmosphere in trace amounts
Why do we need to measure the background radiation count in a room before carrying out an experiment?
To get a more accurate reading that is not impacted by any radiation sources that could be present due to the experiment
Which source of background radiation contributes the most to the overall total?
Radon gas
Which source of background radiation contributes the least to the overall total?
nuclear power and weapons
What is the percentage of background radiation that comes from rocks and buildings?
14%
Which form of background radiation is largely caused by absorption of the radioisotope carbon 14?
rocks and buildings
Which type of background radiation would increase if you were in an aero-plane?
Cosmic rays
Why might accident prone people end up being exposed to more radiation than other people?
Because if they need an X-ray they will absorb the radiation from the x-ray
