<Tr> <Td> Valence electron configuration </Td> <Td> 2s </Td> <Td> 3s </Td> <Td> 4s </Td> <Td> 5s </Td> <Td> 6s </Td> <Td> 7s </Td> </Tr> <Tr> <Td> Core electron configuration </Td> <Td> (He) </Td> <Td> (Ne) </Td> <Td> (Ar) </Td> <Td> (Kr) </Td> <Td> (Xe) </Td> <Td> (Rn) </Td> </Tr> <Tr> <Td> Oxidation states </Td> <Td> + 2, + 1 </Td> <Td> + 2, + 1 </Td> <Td> + 2, + 1 </Td> <Td> + 2, + 1 </Td> <Td> + 2 </Td> <Td> + 2 </Td> </Tr> <Tr> <Td> Melting point </Td> <Td> 1560 K (1287 ° C) </Td> <Td> 923 K (650 ° C) </Td> <Td> 1115 K (842 ° C) </Td> <Td> 1050 K (777 ° C) </Td> <Td> 1000 K (727 ° C) </Td> <Td> 973 K (700 ° C) </Td> </Tr>

Which of the following belong to a category called the main group of elements