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SECTION B: INORGANIC CHEMISTRY
3. (a) This question concerns the elements across period 3 of the periodic table (Na - Ar).
(i) Sketch a graph for the variation of first ionization energy against atomic number for the elements.
- The graph generally shows an increasing trend across the period due to increasing nuclear charge and decreasing atomic radius.
- There are drops at Aluminium (Al) and Sulfur (S) due to electron configuration effects.
- The drop from Magnesium (Mg) to Aluminium (Al) is because Al has its outermost electron in a 3p orbital, which is higher in energy and shielded by the 3s2 electrons, making it easier to remove than a 3s electron from Mg.
- The drop from Phosphorus (P) to Sulfur (S) is because S has a paired electron in one of its 3p orbitals. Removing this paired electron (which experiences repulsion) is easier than removing an unpaired electron from the half-filled 3p subshell of P.
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