<Tr> <Th> Nonmetals </Th> <Td> <Ul> <Li> Polyatomic nonmetals </Li> <Li> Diatomic nonmetals </Li> <Li> Noble gases </Li> </Ul> </Td> </Tr> <Ul> <Li> Polyatomic nonmetals </Li> <Li> Diatomic nonmetals </Li> <Li> Noble gases </Li> </Ul> <Tr> <Th> Other sets </Th> <Td> <Ul> <Li> Nutritional elements </Li> <Li> Platinum - group metals (PGM) </Li> <Li> Rare - earth elements </Li> <Li> Refractory metals </Li> <Li> Precious metals </Li> <Li> Coinage metals </Li> <Li> Noble metal </Li> <Li> Heavy metals </Li> <Li> Native metals </Li> <Li> Transuranium elements </Li> <Li> Transactinide elements </Li> <Li> Major actinides </Li> <Li> Minor actinides </Li> </Ul> </Td> </Tr> <Ul> <Li> Nutritional elements </Li> <Li> Platinum - group metals (PGM) </Li> <Li> Rare - earth elements </Li> <Li> Refractory metals </Li> <Li> Precious metals </Li> <Li> Coinage metals </Li> <Li> Noble metal </Li> <Li> Heavy metals </Li> <Li> Native metals </Li> <Li> Transuranium elements </Li> <Li> Transactinide elements </Li> <Li> Major actinides </Li> <Li> Minor actinides </Li> </Ul>

Why do families on the periodic table have similar properties