Succeeding in the Frcr Part 1 Exam

Chapter 1 Basic Atomic Structure, Radioactive Decay Please answer all questions True or False. There is no negative marking. 1. Concerning the nucleus of atoms a. It is made up of protons and electrons b. It is made up of protons and neutrons c. Nucleons are held together by the strong nuclear force d. The mass number represents the number of protons e. The number of protons and neutrons is always equal The nucleus of an atom is composed of protons and neutrons. The charge of protons is +1 and it is 0 for neutrons. The strong nuclear force is responsible for holding the nucleus together. The mass number represents the number of protons and neutrons, whereas it is the atomic number that represents the number of protons only. The number of protons and neutrons is not always equal, and for higher atomic number elements neutrons tend to outnumber protons. 1a. False – it is made of protons and neutrons 1b. True – it is made of protons and neutrons 1c. True – the strong nuclear force holds nucleons (protons and neutrons) together 1d. False – the mass number is the number of protons and neutrons 1e. False – the number of protons and neutrons is not always equal FRCR- 1 11/14/09 9:59:45 AM 2 Succeeding in the FRCR Part 1 Exam 2. Concerning Electrons a. In the Bohr model of atomic structure electrons orbit the nucleus b. The electron has +1 charge c. The binding energy of the L-shell is higher than the K-shell d. The K-shell can hold 2 electrons e. Electrons have a greater mass than protons In the Bohr model of the nucleus electrons orbit the nucleus in discrete energy shells. These energy shells start with the letter K and increase alphabetically, e.g. K,L,M,N,O, etc. Each shell holds a certain number of electrons. The energy required to remove an electron from its shell is referred to as the Electron Binding Energy. This is greatest for the inner shell electrons (K-shell) and decreases the further away the electron is from the nucleus. Electrons have a smaller mass than protons, at approximately 9.1 ¥ 10–31 Kg. The mass of a proton is approximately 1836 times greater than this. 2a. True – in the Bohr model electrons orbit the nucleus 2b. False – the electron has a charge of -1 2c. False – the binding energy for the K-shell is higher than for the L-shell 2d. True – the K-shell can hold 2 electrons 2e. False – protons have much greater mass than electrons FRCR- 2 11/14/09 9:59:46 AM Basic Atomic Structure, Radioactive Decay 3 3. Concerning the atomic of tungsten a. It has an atomic number of 74 b. It has a physical density of approximately 19 c. The K-shell binding energy of tungsten is 20 d. The mass number of tungsten is 284 e. It is represented by the letter W Tungsten is an important element in radiology as it is used to produce X-rays. It is represented by the letter W. It has an atomic number of 74 and mass number 184 (110 neutrons). The K-shell binding energy of tungsten is 69.5 KeV. Molybdenum has a K-Shell binding energy of 20.0 KeV. 3a. True – atomic number is 74 3b. True – tungsten has a physical density of approximately 19 3c. False – the K-shell binding energy for Tungsten is 69.5 KeV 3d. False – the mass number for Tungsten is 184 3e. True – it is represented by the letter W on the periodic table FRCR- 3 11/14/09 9:59:46 AM 4 Succeeding in the FRCR Part 1 Exam 4. Concerning the isotopes of an element a. They have the same number of neutrons b. They have the same physical properties c. They have the same chemical properties d. All isotopes are stable e. I123 decays by emitting gamma rays Isotopes of an element have the same number of protons and different numbers of neutrons. They have similar chemical properties and different physical properties. Not all isotopes are stable and hence they can be used in imaging using radio-nuclides. Iodine 123 decays by emitting 160 KeV Gamma rays and it is used in the imaging of the thyroid gland. 4a. False – isotopes have different numbers of neutrons 4b. False – they have different physical properties 4c. True – they have the same chemical properties 4d. False – not all isotopes are stable 4e. True – I123 decays by gamma emission FRCR- 4 11/14/09 9:59:46 AM Basic Atomic Structure, Radioactive Decay 5 5. Concerning nuclides a. Unstable nuclides are called radionuclides b. Nuclides with the same number of protons are called Isotopes c. Nuclides with the same number of neutrons are called Isobars d. Isobars have the same atomic mass numbers e. An Isomer is a nucleus in an unexcited state Isotopes have the same number of protons. Isotones have the same number of neutrons. Isobars have the same atomic mass numbers. An Isomer is the excited state of a nucleus. 5a. True – unstable nuclides are termed radionuclides 5b. True – isotopes have the same number of protons but a different number of neutrons 5c. False – nuclides with the same number of neutrons are called isotones 5d. True – isobars have the same atomic mass number 5e. False – an Isomer is a nucleus in an excited state FRCR- 5 11/14/09 9:59:46 AM 6 Succeeding in the FRCR Part 1 Exam 6. Regarding radioactive half-life a. It is constant for a particular radionuclide b. Decay is a stochastic event c. Half-life is defi ned as the time taken for half the material to decay d. Half-life is directly proportional to the Decay Constant e. One Curie is one transformation per second Radioactive half-life is the time taken for half the material to decay. The decay constant is equal to 0.693/half-life. The Activity is the number of transformations in unit time. The Becquerel is 1 transformation per second. The Curie is 3.7 ¥ 1010 transformations per second. Radioactive decay is an exponential process and as such the activity will NEVER become 0. 6a. True – for a particular radionuclide the half-life is constant 6b. True – radioactive decay is a stochastic event 6c. True – this is the defi nition 6d. False – it is inversely proportional to the half-life 6e. False – a Becquerel is one transformation per second FRCR- 6 11/14/09 9:59:46 AM Basic Atomic Structure, Radioactive Decay 7 7. Concerning Alpha decay a. It occurs only in light nuclei b. It results in the atomic number decreasing by 4 c. The alpha particle is equal to the hydrogen nucleus d. Alpha particles have an energy between 4 and 7 MeV e. It does not occur in nature The alpha particle consists of 2 neutrons and 2 protons. It is the equivalent of a Helium nucleus. It generally occurs with heavy atoms with atomic numbers greater than 82. Alpha particles have a high energy and as such are very damaging to living tissues. They carry a charge of +2 and can travel up to 10cm in air. In tissues they travel less than 0.1 mm. They have an energy between 4-7MeV. They cause the atomic number to fall by 2 and the atomic mass number to fall by 4. 7a. False – it occurs in heavy nuclei 7b. False – the atomic number decreases by 2 7c. False – the alpha particle is the equivalent to a helium nucleus 7d. True – they do have an energy between 4-7MeV 7e. False – alpha decay does occur in nature FRCR- 7 11/14/09 9:59:46 AM 8 Succeeding in the FRCR Part 1 Exam 8. Concerning beta plus decay a. It is also called positron emission b. It occurs in nuclei that are neutron rich c. The atomic number decreases by 1 d. A neutron is emitted with the positron e. A positron has a charge of – 1 Beta plus decay is also called positron emission decay. A positron is an electron with a +1 charge and is a form of anti-matter. It occurs in nuclei which are neutron poor. A proton is converted to a neutron and positron which is ejected from the atom. In addition to the positron a neutrino (not a neutron) is ejected. 8a. True – beta plus decay is also called positron emission 8b. False – it occurs in neutron poor nuclei 8c. True – the atomic number decreases by 1 8d. False – the neutron is not emitted 8e. False – a positron has a charge of +1 FRCR- 8 11/14/09 9:59:46 AM Basic Atomic Structure, Radioactive Decay 9 9 Regarding positrons a. Positrons have a mass equal to electrons b. They annihilate with electrons and release one 511 KeV photon c. Fluorine18 (F18) is a positron emitter d. Elements that decay by positron emission have long halflives e. Positrons only exist while they have kinetic energy Positrons only exist while they have kinetic energy. When they come to rest they spontaneously annihilate with an electron. The mass of the positron and the electron is converted into two photons with energy of 511 KeV that are emitted in exact opposite directions (180 degrees apart.) Some important positron emitters are F18, O15 and C11. Positron emitters generally have short T1/2. 9a. True – positrons and electrons have the same mass but opposite charge 9b. False – two photons are released 9c. True – F18 is a positron emitter 9d. False – they tend to have short half-lives 9e. True – positrons only exist while they have kinetic energy FRCR- 9 11/14/09 9:59:46 AM 10 Succeeding in the FRCR Part 1 Exam 10. Concerning beta minus decay a. Phosphorus32 (P32) is a pure beta minus emitter b. Beta minus decay occurs in neutron-rich radionuclides c. The electrons are emitted from the orbital shells d. The atomic number increases by 1 e. An anti-neutrino is emitted alongside the electron In beta minus decay, a neutron in the nucleus is converted to a proton. An electron and an anti-neutrino are ejected in the process. This process occurs in neutron-rich nuclei. The electrons released have a wide range of energies up to a maximum dependent on the emmiting nuclide. The mass number remains the same, but the atomic number will increase by 1. 10a. True – P32 is a pure beta minus emitter 10b. True – it occurs in neutron rich radionuclides 10c. False – the electrons are ejected from the nucleus 10.d True – the atomic number increases by 1 10.e True – an anti-neutrino is ejected alongside the electron