Question 9.
Write down the electronic configuration of the following elements from the given atomic numbers. Answer the following question with explanation.
19K, 3Li, 11Na, 4Be
Which of these atoms has smallest atomic radius?
Answer:
Electronic configuration:
⇒ The atomic number of potassium = 19
The electronic configuration of 19K = 2,8,8,1
⇒ The atomic number of lithium = 3
The electronic configuration of 3Li = 2,1
⇒ The atomic number of sodium = 11
The electronic configuration of 11Na = 2,8,1
⇒ The atomic number of beryllium = 4
The electronic configuration of 4Be = 2,2
Among the given elements, Be has the smallest atomic radius.
Explanation:
⇒ Atomic radius goes on decreasing along a period.
⇒ Atomic radius goes on increasing along a group.
⇒ By combining these two facts, we can conclude that Be has the smallest atomic radius.
