## Chemistry 9th Edition

a. $Be < Na < Rb$ b. $Ne < Se < Sr$ c. $O < P < Fe$
a. As you go downwards in the periodic table, the atomic radius increases because orbital size increases with an increase in the principal quantum number, n. Therefore, the order by the periodic table is $Be < Na < Rb$. b. As you go downwards in the periodic table, the atomic radius increases because orbital size increases with an increase in the principal quantum number, n. Therefore, the order by the periodic table is $Ne < Se < Sr$. c. As you go downwards in the periodic table, the atomic radius increases because orbital size increases with an increase in the principal quantum number, n. Therefore, the order by the periodic table is $O < P < Fe$.