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State the relative charges and relative masses of a proton, a neutron and an electron.
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proton has charge +1 and relative mass 1; neutron has charge 0 and relative mass 1; electron has charge −1 and relative mass / negligible
An ion of sulfur is represented by ³²₁₆S²⁻. Determine the numbers of protons, neutrons and electrons in this ion.
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protons = 16; neutrons = 32 − 16 = 16; electrons = 16 + 2 = 18
Beams of protons, electrons and neutrons travel at the same velocity through an electric field. Describe and explain how each beam is deflected.
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protons deflected towards the negative plate; electrons deflected towards the positive plate by a much larger angle; neutrons not deflected; magnitude of deflection depends on charge-to-mass ratio / electrons have far higher charge-to-mass ratio than protons / neutrons have no charge so experience no force
Explain why the atomic radius of magnesium is greater than that of sulfur.
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both elements are in Period 3 / outer electrons in same shell; sulfur has more protons / greater nuclear charge; shielding is approximately the same across the period; outer electrons in sulfur pulled more strongly towards the nucleus / smaller radius
Discuss the variation in atomic radius across Period 3 and down Group 2, explaining the trends in terms of nuclear charge and shielding.
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across Period 3 atomic radius decreases; nuclear charge increases by one proton per element; electrons added to the same outer (third) shell; shielding by inner shells remains approximately constant; effective nuclear attraction on outer electrons increases; outer electrons pulled closer to the nucleus; down Group 2 atomic radius increases; each successive element has one additional occupied electron shell; outer electrons are further from the nucleus; inner shells provide greater shielding; net attraction on outer electrons decreases despite higher nuclear charge