The second ionisation energies are higher than the first ionisation energies. This is mainly due to β Periodic Table and Periodicity Chemistry Question
Question
The second ionisation energies are higher than the first ionisation energies. This is mainly due to the fact that after the removal of the first electron, the atom changes into monovalent positive ion. In the ion, the number of electrons decreases but the nuclear charge remains the same. As a result of this, the remaining electrons are held more tightly by the nucleus and it becomes difficult to remove the second electron. Therefore , the value of second ionisation energy. (IE2), is greater than that of the first ionisation energy (IE1). Similarly third ionisation energy (IE3) is greater than that of second IE2.

π‘ Solution & Explanation
Step 1: Relate the atomic numbers to the nearest noble gases in the periodic table. Radon (Rn) has Z=86, and the 7th period ends with the noble gas Oganesson (Og) at Z=118 in Group 18. Step 2: The element with atomic number Z=117 lies immediately before Oganesson (Z=118) in the 7th period, which places it in Group 17 (the halogens). Step 3: The element with atomic number Z=120 will belong to the 8th period. The alkali metal of Group 1 will be Z=119, and the alkaline earth metal of Group 2 will be Z=120. Thus, they belong to groups 17 and 2.