Determine the number of inner and valence electrons in an atom of the given elements.
a. O
b. C
c. Fe
d. Mg
e. S

O = 2, 8; C = 2, 4; Fe = 20, 4; Mg = 6, 6, S = 10, 2

O = 2, 6; C = 2, 4; Fe = 24, 2; Mg = 10, 2, S = 10, 6

O = 2, 8; C = 2, 6; Fe = 18, 8; Mg = 8, 6, S = 10, 2

O = 2, 8; C = 2, 6; Fe = 18, 6; Mg = 10, 2, S = 10, 8