This configuration Kr 5s 4d" has each electron outside the Kr core in a separate orbital and has the maximum number of electrons with parallel spins (6), In Mo, this configuration has a lower energy than [Kr) 5e 4d The greater stability of the configuration is also found in the case of Cr (directly above Mo), but W (below Mo) has an s configuration. In Cr and Mo, the ns and (n-1)d subshells are sufficiently in energy so that electron pairing is avoided.