How is the electron configuration of chromium different?
The electron configuration of chromium is different because it contains five 3d electrons and one 4s electron, rather than four 3d electrons and two 4s electrons.
Electron configurations are determined experimentally. The electron configuration for chromium is
There are many transition metals that have unpredicted electron configurations, determined experimentally.
You can print a periodic table that has the electron configurations of the elements from here: https://www.vertex42.com/ExcelTemplates/periodic-table-of-elements.html