<Tr> <Th_colspan="26"> 41 Nb niobium: (Kr) 4d 5s </Th> </Tr> <Tr> <Td> 1s </Td> <Td> 2s </Td> <Td> 2p </Td> <Td> 3s </Td> <Td> 3p </Td> <Td> 3d </Td> <Td> 4s </Td> <Td> 4p </Td> <Td> 4d </Td> <Td> </Td> <Td> 5s </Td> <Td> </Td> <Td> </Td> <Td> </Td> <Td> </Td> <Td> </Td> <Td> </Td> <Td> </Td> <Td> </Td> <Td> </Td> <Td> </Td> <Td> </Td> <Td> </Td> <Td> </Td> <Td> </Td> <Td> </Td> </Tr> <Tr> <Td> </Td> <Td_colspan="2"> 8 </Td> <Td_colspan="3"> 18 </Td> <Td_colspan="4"> 12 </Td> <Td_colspan="5"> </Td> <Td_colspan="4"> </Td> <Td_colspan="3"> </Td> <Td_colspan="2"> </Td> <Td_colspan="2"> </Td> </Tr> <Tr> <Th_colspan="26"> 42 Mo molybdenum: (Kr) 4d 5s </Th> </Tr>

What is the last number in the electronic configuration of a group 7 element