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Descrição
| Questão | Responda |
| Name the three subatomic particles of an atom. | Protons Neutrons Electrons |
| Where in an atom are protons found? | Inside the nucleus. |
| Where in an atom are neutrons found? | Inside the nucleus. |
| Where are electrons found? | Electrons are located in electron shells, orbiting around the nucleus. |
| What is the mass of a proton? | The mass of a proton is 1. |
| What is the mass of a neutron? | The mass of a neutron is 1. |
| What is the mass of an electron? | For WJEC GCSE Physics an electron is considered to be so small it has a mass of 0. |
| What is the charge on a proton? | The charge on a proton is +1. |
| What is the charge on a neutron? | The charge on a neutron is 0. |
| What is the charge on an electron? | The charge on an electron is -1. |
| What is an isotope? | Isotopes are atoms of the same element which have different number of neutrons. Isotopes of an element have the same proton number but differing mass / nucleon number. |
| Atomic number (also know as proton number) = 53 Therefore there are 53 protons in the nucleus of an atom of iodine-123. | |
| Atomic number = 53 Therefore there are 53 electrons in an atom of iodine-123. | |
| Mass number (also know as neutron number) is the number of protons PLUS the number of neutrons = 123 Atomic number (also know as proton number) = 53 Therefore 123 - 53 = 70 neutrons | |
| Atomic number (also know as proton number) = 53 Therefore there are 53 protons in the nucleus of an atom of iodine-131. | |
| Atomic number = 53 Therefore there are 53 electrons in an atom of iodine-131. | |
| Mass number (also know as neutron number) is the number of protons PLUS the number of neutrons = 131 Atomic number (also know as proton number) = 53 Therefore 131 - 53 = 78 neutrons | |
| What causes an atom to be radioactive? | If an atom has an imbalance of protons and neutrons in the nucleus it will be also be UNSTABLE. The nucleus tries to become stable by breaking up into stable fragments. This process is RADIOACTIVE DECAY. |
| Name the 3 types of radiation emitted from the nucleus. | Alpha ( α ) radiation Beta (β) radiation Gamma (γ) radiation |
| What is Alpha ( α ) radiation? | A helium nucleus (2 protons and 2 neutrons). |
| What is Beta (β) radiation? | A fast moving, very high energy electron. |
| What is Gamma (γ) radiation? | An extremely high energy electromagnetic wave. |
| Describe the penetrating power of Alpha ( α ) radiation and what can stop it. | Alpha ( α ) radiation has the lowest penetrating power and can only penetrate (travel through) a few cm of air and is stopped by a thin sheet of paper or skin. |
| Describe the penetrating power of Beta (β) radiation and what can stop it. | Beta (β) radiation radiation has medium penetrating power and can penetrate (travel through) up to a metre of air and is stopped by a few mm of aluminium. |
| Describe the penetrating power of Gamma (γ) radiation and what can stop it. | Gamma (γ) radiation radiation has the highest penetrating power and and can travel through most materials and requires several cm of lead of several meters of concrete to stop it. |
| Describe the ionising power of Alpha ( α ) radiation. | Very high – most damaging inside the body. |
| Describe the ionising power of Beta (β) radiation. | Medium |
| Describe the ionising power of Gamma (γ) radiation. | Low ionising power compared with alpha and beta radiation. Easily passes through the body. |
| ALPHA DECAY: Balance the following nuclear equations by calculating the value of a, b, c and d. | During alpha decay the number of protons decreases by 2 and the number of neutrons decreases by 2. Therefore the proton number decreases by 2 and the nucleon number decreases by 4. a = 237, b 93, c = 232, d= 82 |
| BETA DECAY: Balance the following nuclear equations by calculating the value of a, b, c and d. | During beta decay the number of protons increases by 1 and the number of neutrons decreases by 1. Therefore the proton number increases by 1 and the nucleon number stays the same. a = 2, b = 1, c = 63, d = 29 |
| What is ionising radiation? | Some radioactive particles and electromagnetic waves have enough energy to rip electrons away from atoms and molecules. Ions are formed which can interact with cells in the body and damage DNA/cells. This damage can lead to the formation of cancer. |
| Describe why radioactive decay is described as a totally random and spontaneous process. | Some atoms are unstable and so we say that they are radioactive. They try to become stable emitting alpha, beta or gamma radiation. The process of atoms undergoing radioactive decay is totally random and spontaneous because there is no way of telling when or which atom will decay next in a radioactive material. |
| Types of ionising radiation include: | Alpha, beta, gamma, x-rays and ultraviolet. |
| Types of non-ionising radiation include: | Visible light, infrared, microwave and radio waves. |
| The following information is recorded about A radioactive material. determine the type and amount of each radiation emitted by the radioactive material. | - The count drops from 250 to 50 with a sheet of paper. This indicates the presence of alpha radiation. Count rate alpha = 250 – 50 = 200 counts. - Placing aluminium in front has no effect so there is no beta radiation present. - The lead decreases the counts so gamma radiation must be present. Count rate gamma = 50 – 0.5 = 49.5 counts. - Background count = 0.5 counts as all (almost) gamma radiation should be stopped by 20cm of lead. ANSWERS: alpha = 200 count/s, beta = 0 count/s, gamma = 49.5 count/s, background = 0.5 count/s |
| What is radon gas? | Radon gas is formed when uranium in volcanic rocks like granite undergoes radioactive decay to form radium and then the radium decays to radon gas. High levels of radon gas can lead to lung cancer. |
| List 4 ways to protect people and the environment from radiation sources. | 1. Limiting time 2. Distance 3. Shielding 4. Containment |
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