Which of these would be most attracted to a magnet?

1s2 2s2 2p6 3s2 3p6 4s2 3d10

1s2 2s2 2p6 3s2

1s2 2s2 2p6 3s2 3p6 4s2 3d5

1s2 2s2 2s6 3s2 3p6

The one that is the most attracted to a magnet is the element with an electron configuration that has the most number of unpaired electrons. In this case, 3d10 is already full hence no unpaired electrons, as well as 3s2 and 3p6. 3d5 does not have a full octet, hence the answer is C

1s2 2s2 2p6 2s2 3p6 4s2 3d5