Question

Which of the following atomic number has bigger size than aluminium atom?

• A. $12$
• B. $14$
• C. $16$
• D. $17$

Answer 1

Answer: (A)

$12$

Elements having atomic number $12,14,16,17$ and aluminium (atomic no. $13$) belong to same period. For elements belonging to same period, atomic radius decreases on going from left to right due to increase in effective nuclear charge. Thus, lower the atomic number greater the size in a period. Therefore, element with atomic number 12 may have size greater than that of aluminium.