What is the complete ground state electron configuration for the selenium atom?

Se

1s² 2s²2p⁶ 3s²3p⁶ 4s²3d¹⁰3p⁴

You can do it just follow the periodic table

1) groups 1 and 2 give s-electrons, and number of the level equals number of the period

2) groups from 13 to 18 give p-electrons, and number of the level equals number of the period

3) groups from 3 to 12 give d-electrons and level one less than number of the period