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Rationalize the following main-group observations. Make sure you touching on the physical origins of these observations. - elemental oxygen exists as diatomic molecules held together by 121-pm O-O bonds, whereas elemental sulfur exists as eight-atom rings held together by 205pmSS bonds - sulfur has a more positive electron affinity (279kJmol1) than oxygen (249kJmol1) - unlike phosphorus, arsenic, and antimony, bismuth does not form a pentachloride - lithium is the only alkali metal that forms a stable nitride ( Li3N). Magnesium, as well a other alkaline earth metals, also form nitrides