A) Boron, 3 valance electrons
3p1 is in the 3rd period and the first element in the P block (groups 13-18). Valence electrons=the numbers of electrons in the outermost level
B) Iodine, 7 valence electrons
now we’re in the 5 period in the p block. The 5th element in the p block is Iodine and it’s outermost levels, 5s2 and 5p5 add up to 7 valence electrons
C) calcium, 2 valence electrons
In the 4th period and 2nd group
Outermost level, 4s2, has 2 electrons
D) indium
Located at 5p1, 5th period and the 1st element of the p block.
Outermost level is 5s2 and 5p1 which adds up to 3 electrons
E) selenium, 6 valence electrons
Count all the dots and those are the valence electrons