Question
Identify the elements of alkali metals and alkaline earth metals respectively having highest 1st ionization enthalpy.
MHT CET
Chemistry
s Block Elements
2026
MHT CET 2026 (13 April Shift 2)
MHT CET Chemistry Question (2026) — Solution
Options
- A. K and Ca
- B. Li and Be
- C. Rb and Ba
- D. K and Sr
Answer
B. Li and Be
Step-by-step solution
Ionization enthalpy decreases down a group in the periodic table due to an increase in atomic size and shielding effect. Among alkali metals (Group 1), Lithium ( Li ) is at the top of the group and has the smallest atomic size, hence it has the highest first ionization enthalpy. Among alkaline earth metals (Group 2), Beryllium ( Be ) is at the top of the group and has the smallest atomic size, hence it has the highest first ionization enthalpy. Therefore, the elements with the highest first ionization enthalpy are Li and Be respectively. Answer: Li and Be
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