What is the ground state shorthand notation for manganese (Mn) ?

The ground state short hand notation of manganese would be [Ar] 3d5 4s2. The atomic number of this element is 25. We use this value to write the electronic configuration. The complete configuration would be written as 1s2 2s2 2p6 3s2 3p6 3d5 4s2. Adding the expoenents of each subshell, we would get a value of 25. By looking at the configuration, a part of it represents a certain element, a noble gas. In this case, it is the noble gas argon with the electronic configuration 1s2 2s2 2p6 3s2 3p6. So, we can write the configuration of manganese as [Ar] 3d5 4s2.