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Constituents of the atom questions
A proton, a neutron and an electron, plus two numbers and one notation, are everything the atom's description needs. Add the idea of specific charge and a single division narrows down what any mystery nucleus, ion or particle can be.
19 original questions · 54 marks · the constituents of the atom notes · Particles
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State the charge and the relative mass of the proton, the neutron and the electron.
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Proton: charge +1.60 × 10−19 C, relative mass 1. Neutron: charge 0, relative mass 1 (1). Electron: charge −1.60 × 10−19 C, relative mass about 1/1836 (1).Calculate the specific charge of a proton (e = 1.60 × 10−19 C, mp = 1.67 × 10−27 kg).
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Specific charge = Q/m = (1.60 × 10−19)/(1.67 × 10−27) (1)
= 9.58 × 107 C kg−1 (1)Explain what is meant by two isotopes of an element.
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Isotopes are atoms of the same element, so with the same number of protons and the same Z (1), that have different numbers of neutrons and so different mass numbers A (1).The nuclide of copper used in electrical wiring is written 6329Cu. State what the number 63 and the number 29 each represent.
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63 is the nucleon number A, the total number of protons and neutrons in the nucleus (1). 29 is the proton number Z, the number of protons (1).State the specific charge of the neutron. Explain your answer.
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Zero (1). Specific charge is charge divided by mass, and the neutron has mass but no charge, so Q/m = 0 (1).State one use of isotopic data.
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Carbon dating: the ratio of carbon-14 to carbon-12 in dead material falls with age, so measuring it dates archaeological finds (1). (Accept any valid use, e.g. identifying the origin of a sample from its isotopic signature.)Calculate the specific charge of an electron (me = 9.11 × 10−31 kg), and comment on how it compares with that of a proton.
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Specific charge = (1.60 × 10−19)/(9.11 × 10−31) (1)
= 1.76 × 1011 C kg−1 (1)
Far larger than the proton's, because the electron has the same magnitude of charge but a much smaller mass (1)A nucleus is written 146C. State the number of protons and neutrons it contains, and the number of electrons in the neutral atom.
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Protons: 6, since Z = 6 (1). Neutrons: A − Z = 14 − 6 = 8 (1). The neutral atom has 6 electrons (1).Calculate the specific charge of an alpha particle (a helium-4 nucleus: charge +2e, mass ≈ 4mp).
An oxygen-16 atom loses two electrons to become an ion of charge +2e. Calculate the specific charge of this ion (mass ≈ 16mp).
A bare nucleus produced in an ion source has a charge of +4.80 × 10−19 C and a mass of 1.17 × 10−26 kg. The candidate nuclides are helium-4 (Z = 2), lithium-7 (Z = 3), beryllium-9 (Z = 4) and boron-11 (Z = 5). Determine which nuclide it is (e = 1.60 × 10−19 C; nucleon mass = 1.67 × 10−27 kg).
In an electrostatic paint sprayer, a paint droplet of mass 2.4 × 10−15 kg acquires a specific charge of 2.0 × 10−4 C kg−1 by losing electrons. Calculate the charge on the droplet and hence the number of electrons removed (e = 1.60 × 10−19 C).
Chlorine has two stable isotopes, 3517Cl and 3717Cl. State the number of protons and the number of neutrons in each nucleus, and explain why the two isotopes have identical chemical properties.
A uranium nucleus is written 23892U. State the number of protons and neutrons, and calculate the specific charge of the nucleus (mass ≈ 238mp).
Compare the specific charge of a single proton (a hydrogen-1 nucleus) with that of an alpha particle by calculating both, and state which is greater.
Explain why the electron has by far the largest specific charge of the three sub-atomic particles.
A helium-3 nucleus contains 2 protons and 1 neutron. Show that the specific charge of a helium-3 nucleus is about 6 × 107 C kg−1. Go on to explain why this is greater than the specific charge of a helium-4 nucleus (e = 1.60 × 10−19 C; nucleon mass = 1.67 × 10−27 kg).
A mass spectrometer identifies ions by their specific charge. A singly ionised neon atom is measured to have a specific charge of 4.36 × 106 C kg−1. Neon has two common isotopes, neon-20 and neon-22. Deduce which isotope the measured ion is. Treat the mass of an ion of nucleon number A as A × 1.67 × 10−27 kg; e = 1.60 × 10−19 C.
Explain why no bare nucleus can have a specific charge greater than that of a single proton. Treat the proton and neutron masses as equal.
The same practice on paper: the printable workbook for this topic, questions and a worked answer book.
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