1s22s22p63s23p63d104s24p65s2 what element is it​

go to this periodic table

http://www.ptable.com/

click on the orbitals tab

mouse around until you get familiar with the filling patterns. look for

.. (1) what electrons fill in the left two columns

.. (2) what electrons fill in the right 6 columns

.. (3) what electrons fill in the transition metals

.. (4) what electrons fill in the actinide and lathanide series

.. (5) when electrons "pair up"

.. (6) look for deviations in the patterns.. columns 6 and 11 for example

.. .. . .note.. half filled d orbitals are lower energy than partially filled d + filled s

.. .  .. so the "s" electrons are borrowed.

you should be able to see this

.. 1s2 2s2 2p6 2s2 3p6 3d10 4s2 4p6 5s2 .. .<=== 5s2

and find strontium.. row 5... 2 of the s electrons..

mark me brill

the answer is b)3/8x+1