Chemistry Regent Exam August 2022

7. Compared to the number of electron shells and radius of an aluminum atom in the ground state, a boron atom in the ground state has

(1) fewer electron shells and a smaller radius

(2) fewer electron shells and a larger radius

(3) more electron shells and a smaller radius

(4) more electron shells and a larger radius

Explanation: Let's first find Aluminum and Boron on the Periodic Table on our reference table. Aluminum (Al) is number 13 and boron (B) is number 5.

Aluminum is in the third period (row) and has 3 electron shells while boron is in the second period and has 2 electron shells. Therefore, boron has fewer electron shells. Less electron shells means smaller radius.

Atomic radius increases up and to the right. Alternatively, you can actually look up atomic radius in Table S for each element and compare the two element given.

Answer: 1