1. Tardigrade
  2. Question
  3. Chemistry
  4. Alkaline-earth metals form dipositive ions, instead of unipositive ions, because

Question Error Report

Thank you for reporting, we will resolve it shortly

Back to Question

Q. Alkaline-earth metals form dipositive ions, instead of unipositive ions, because

NTA AbhyasNTA Abhyas 2020The s-Block Elements

Solution:

Alkaline-earth metals form dispositive ions, instead of unipositive ions, because the hydration energy of dipositive ions compensates the higher value of second ionization energy.

Heat of hydration of an ion depends upon the charge/radius ratio. Compared to the heats of hydration of alkali metal ions of comparable size, the heats of hydration of alkaline-earth metal ions are approximately four times greater, e.g., $\Delta H_{h y d}Na^{+}$ (size 102 pm)

$=-397$ kJ/mol; $\Delta H_{h y d}Ca^{2 +}$ (size 100 pm)

$=-1650$ kJ/mol.