Introduction to Chemistry
Chromium does not promote any electrons, resulting in 4s2 3d4.
Chromium promotes an electron from the 3d orbital to the 4s orbital, resulting in 4s2 3d4.
Chromium promotes an electron from the 4s orbital to the 3d orbital, resulting in 4s1 3d5.
Chromium promotes an electron from the 4p orbital to the 3d orbital, resulting in 4s2 3d5.