Chapter 7 - Atomic Structure and Periodicity - Exercises - Page 346: 109

a. He b. Cl c. Element 116 d. Si e. $Na^{+}$

a. Atomic radius tends to decrease as we go across a period due to increased effective nuclear charge or proton pull. Therefore, $He$ has the smallest radius. b. Atomic radius tends to decrease as we go across a period due to increased effective nuclear charge or proton pull. Atomic radius also tends to increase going down a group due to more principal energy levels. Therefore, $Cl$ has the smallest radius. c. Atomic radius tends to decrease as we go across a period due to increased effective nuclear charge or proton pull. Atomic radius also tends to increase going down a group due to more principal energy levels. Therefore, Element 116 has the smallest radius. d. Atomic radius tends to decrease as we go across a period due to increased effective nuclear charge or proton pull. Atomic radius also tends to increase going down a group due to more principal energy levels. Therefore, $Si$ has the smallest radius. e. Atomic radius is smaller in cations than in neutral or anions due to a greater effective nuclear charge or proton pull. Therefore $Na^+$ has the smallest radius.