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Mark 7 (a) (i) Atom R is located in Group 17, Period 3 1 + 1 (ii) Electron arrangement of atom R is 2.8.7. Group 17 because it has seven valence electron. Period 3 because it has three shells filled with electron 1 1 1 (b) (i) Atoms P and R form covalent bond. To achieve the stable electron arrangement, atom P needs 4 electrons while atom R needs one electron. Thus, atom P shares 4 pairs of electrons with