How many electrons will each element gain in forming an ion?

a. Nitrogen ______
b. Oxygen ________
c. Sulfur _______
d. bromine _______

2 answers

Look for the elements in the periodic table. N is in group 5 (or 15 depending upon thesystem your prof is using) so it has five electrons in its outside shell. It needs 8 to complete the shell; therefore, it will add three electrons to make a N^-3 ion.
Oxygen is in group VI (or 16); it has 6 electrons and needs two more so it adds two to make the oxide -2 ion. Now you do the othersl.
nitrogen=1
oxygen=2
sulfur=2
bromine=1