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Flashcards by Robin Skailes, updated more than 1 year ago
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| Question | Answer |
| Describe the Greek model of the atom in eight words. | Tiny spheres called atoms which were indivisible. |
| Democritus originally came up with which model of the atom? | The Greek model |
| John Dalton agreed with the Greek model but theorised that each element had: (the same/a different) atom. | A different atom. |
| Who was credited with discovering electrons? | J J Thompson |
| What model of the atom did J J Thompson theorise? | Plum pudding model. |
| Who came up with the first nuclear model? | Ernst Rutherford |
| What experiment did Rutherford use to discover the first nuclear model? | Alpha scattering experiment. |
| What results were expected from the alpha scattering experiment and why were they expected? | The expected results were that particles would pass through or for a select few be deflected because of the plum pudding model. |
| How does the prediction of the alpha scattering experiment compare to the results? | They expected particles to pass through or be deflected and they passed through but some deflected more than expected. |
| What did the results of the alpha scattering experiment prove? | 1) Mass was concentrated in the centre. 2) The nucleus had a + charge. 3) Most of the atom was empty space. |
| Niels Bohr suggested that orbiting electrons do so at different distances called what? | Energy levels. |
| James Chadwick proved the existence of which sub atomic particle and what did it help to explain? | Proved existence of neutron to explain the imbalance between the atomic and mass numbers. |
| The nucleus contains which two sub atomic particles? | Protons and neutrons. |
| What charges does each sub atomic particle in a nucleus have and what is the overall charge of a nucleus? | Proton: +1 Neutron: 0 Nucleus: + |
| The radius of the nucleus is about (100/1,000/10,000) times smaller than the radius of the whole atom. | 10,000 |
| Most of an atom is comprised of mostly what? | Empty space. |
| What sub atomic particles orbit the nucleus and what charge do they have? | Electrons with -1 charge. |
| The number of protons is equal to the number of what? Why is this? | Electrons This is because the charges then even out. + and - charges cancel out. |
| What are isotopes? | Isotopes are different forms of the same element. |
| All isotopes have the same number of which sub atomic particle? | Protons |
| The number of protons defines the atomic _____ of an element. | Number |
| The mass number of an atom is the sum of the total of which sub atomic particles? | Protons and neutrons. |
| Isotopes have differing numbers of which sub atomic particle? | Neutrons. |
| How many elements have isotopes? | All of them! hOW maNy Of thOsE aRe sTable? It's a code. Figure it out! |
| What happens to the unstable isotopes and why do they do this? | They decay into other elements and emit radiation as they try to become more stable |
| What is radioactive decay and why does it happen? | Radioactive decay is when isotopes emit radiation while balancing the sub atomic particles to become more stable. |
| What are the three main types of radiation? | Alpha Beta Gamma |
| Alpha particles are what type of nuclei and why is this? | They are helium nuclei as the alpha particles have two protons and two neutrons. |
| How penetrating is alpha radiation? | Low |
| How far does alpha radiation travel? | Around 3-5 cm. Basically just a few cm. |
| What is alpha radiation stopped by? | A sheet of paper. |
| How ionising are they? | Very ionising. |
| Put the types of radiation in terms of ionisation. Starting with the highest. | Alpha Beta Gamma |
| Put the types of radiation in order of distance travelled. Starting with the highest. | Gamma Beta Alpha |
| What is beta radiation? | A fast moving electron. |
| What is gamma radiation? | An electromagnetic wave. |
| Nuclear equations show radioactive _____ by using element symbols. | Decay |
| How are nuclear equations written? | atom before decay ---> atom after decay + radiation emitted. |
| What is the golden rule when writing nuclear equations? | The total mass and atomic numbers must BE THE SAME! |
| Alpha decay __________ the charge and mass of the nucleus. | Decreases. |
| Why does the mass and charge decrease when alpha decay occurs? | Because a helium nuclei is released during alpha decay. |
| When alpha decay occurs, how much is the atomic number and mass number reduced by? | Atomic: 2 Mass: 4 Why do you think this is? |
| Why is the charge reduced during alpha decay? | Because protons are being removed from the isotope. Protons are + charged therefore you are left with a negative charge. |
| Uranium 238 becomes Thorium 234 during alpha decay. Write a nuclear equation to show this. | 238 ---> 234 + 4 92 ---> 90 + 4 U ---> Th + He |
| Beta decay increases the _____ of the nucleus. | Charge |
| Why does beta decay increase the charge of a nucleus? | Because the process involves losing an electron so as a result the charge increases as electrons have a negative charge. |
| Does the mass or charge change during gamma decay? Why or why not? | No because there is no change to atomic mass or number because gamma decay just removes excess energy. |
| Radioactivity is a (controlled/random) process. | Random |
| What is half life? | Half life is the amount of time needed for the radiation emitted to half. (Also called the amount of activity) |
| What is half life measured in? | Becquerels Bq |
| The radioactivity of a source _________ over time. | Decreases |
| When does the activity of a radioactive source reach zero? | It never does. |
| The initial activity of a sample is 640Bq. Calculate the final activity as a percentage of the initial activity after 2 half lives. | 25% |
| How can you measure the half life using a graph? | Find the time interval corresponding to the activity twice and then find the difference of the time intervals. |
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