January 2018 NY Regents Chemistry Exam
34 In which group on the Periodic Table would a nonmetallic element belong if atoms of this element tend to gain two electrons to complete their valence shell?
(2) 15 (3) 16
Solution: If atoms want to gain 2 electrons to complete their valence shell, we are looking for an element with -2 oxidation number (gaining two electrons is gaining two minus charges). We can look at the Periodic Table to see the oxidation numbers. on the top right corner of each element.