Chromium number 24 has 6 valance electrons.
The outer or valance configuration of Chromium is
The atom can lose the 3 d electrons becoming +4. It can lose the 4s electrons become +2, It can lose the 4s and 3d electrons becoming 6+ It can shift one 4s electron into the d orbitals to create a half filled d orbitals resulting in either +1 or + 5.
There are only six valance electrons but they can be combined in multiple ways