Question

an element'X' has a mass number of 27 and it contains 13 protons. write its eletronic configration

Answer 1

atomic no. = no. of protons. = 13.

so it is aluminium.

and its electronic configuration is
1s2, 2s2 2p6 , 3s2 3p1.
or
2,8,3

hope it helps you