3. What are valence electrons? How do you quickly determine the number of valence electrons an
atom has?

Valence electrons are the electrons found in the highest and main energy level of the atom, being these responsible for the interaction between atoms of different species or between atoms of the same species. You can quickly determine these by looking at a periodic table like this one... Which is where the roman numbers come in and show the valence electrons. (THIS TABLE IS IN SPANISH, I hope you still recognize the symbols.) :))

d: the voltage of the secondary coil is less than that of the primary coil.

im not suree sorry if wrong

i believe the answer is true.