Question

What is the predicted order of first ionization energies from highest to lowest for beryllium, calcium, magnesium, and strontium?

Answer 1

Answer: Beryllium(Be) > Mg(Magnesium) > Ca(Calcium) > Sr(Strontium)

Explanation: Ionization energy is defined as the energy which is used to remove an electron from the outermost shell of an element in the gaseous state.

Thus as we move down the group, we can observe that atomic mass is increasing as the number of shells are increasing, thus the outermost shell has less attraction towards the nucleus due to the shielding effect of the penultimate and anti penultimate shells.

Thus the order of the Ionization energy is found to be -

Beryllium(Be) > Mg(Magnesium) > Ca(Calcium) > Sr(Strontium)

Answer 2

We can predict the order of the elements given above according from the highest to lowest first ionization energies by using the trends in a periodic table. For elements in a family, the ionization energy decreases as it goes down. Therefore, the correct order would be Be, Mg, Ca, Sr.