Answer: Option (2) is the correct answer.
Explanation:
Ionization energy is defined as the energy required to remove the most loosely bound electron from a neutral gaseous atom.
And, when we move across a period then there is a decrease in the ionization energy due to decrease in the size of atoms.
Whereas when we move down a group then there is an increase in ionization energy because of increase in size of the atoms.
Since, it is given that each atom has 2 valence electrons therefore, all the atoms belong to group 2.
And, as it has lower first ionization energy than calcium it means the atom is larger in size than calcium atom.
Hence, we can conclude that this element located in Group 2, Period 5 on the periodic table.
