How many dots would appear in the Lewis electron dot diagram for an
atom whose electron configuration ended 4s2 3d10 4p3 ?
a.5   b. 2   c. 15

Hello teatea,

The total number of electrons in the Lewis dot structure for an atom
is the number of electrons in the S and P orbitals of the highest
energy level. There are 2 electrons in the S orbital and 3 in the P
orbital in the 4th energy level, thus there are a total of 5 electrons
in the Lewis dot diagram for the atom you specified.  (The correct
answer is then (a) 5).

This is further explained at the following site: 
http://www2.gasou.edu/chemdept/general/molecule/lewis.htm

Please let me know if you require a further explanation before you
rate this answer.

Thanks,
chis-ga