Discussion Forum



1)

Which of the following represents the correct order of increasing the first ionisation enthalpy for Ca, Ba, S, Se and Ar  ?


A) $Ca\lt S \lt Ba \lt Se \lt Ar$

B) $S\lt Se \lt Ba \lt Ca \lt Ar$

C) $Ba\lt Ca \lt Se \lt S \lt Ar$

D) $Ca\lt Se \lt Ba \lt S \lt Ar$

Answer:

Option C

Explanation:

 Ionisation  energy increases along a period from left to right and decreases down a group. The position of given elements in the periodic table is as

  2  16  18

  Ca S   Ar

    Ba Se

  Thus, the order of increasing  $\triangle H_{IE_{1}} $  is 

  Ba <Ca< Se < S< Ar