Identify the element below and give the symbols of the other elements in its group. [ar]4s23d104p4 element symbol:

[Ar]4s²3d¹⁰4p⁴

We see that the last level is this element is 4, so this element should be in
4th period, it has 4 p-electrons, so it should be in 16th group.
4th period, 16th group - it is Se.

You can also go to the next element after Ar, and count beginning of this element 16. (2+10+4 =16 electrons)
 From "K" (where K is the first) you count to 16 and it is going to be Se.