The second ionisation energies are higher than the first ionisation energies. This is mainly due to — 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.
💡 Solution & Explanation
Step 1: Understand that electropositive character (metallic character) increases moving down a group and decreases moving from left to right across a period. Step 2: Alkali metals (Group 1) are always more electropositive than alkaline earth metals (Group 2) within the same period due to lower ionization energies. Step 3: Among the choices, [He] 2s1 (Lithium) and [Xe] 6s1 (Cesium) are alkali metals. Since Cesium is much further down Group 1 than Lithium, its outermost electron is most easily lost, making [Xe] 6s1 the configuration of the most electropositive element.