WAEC Chemistry 2017 Paper

Concept:Atomic size decreases across a period because the increasing positive charge in the nucleus pulls the same outer shell of electrons closer.Explanation:Moving across a period, electrons are added to the same valence shell.At the same time, the number of protons in the nucleus increases.This causes a steady increase in nuclear charge.The stronger nuclear charge exerts a greater attractive force on the outermost electrons.As a result, the valence electrons are drawn closer to the nucleus.Thus, the atomic radius decreases from left to right across a period.Answer:Option A: nuclear charge increases while the outermost electrons are drawn closer to the nucleus.