Home Preparation for National Talent Search Examination (NTSE)/ Olympiad
Chapter : 7. Periodic Classification of Element
Ionisation Energy and Electron Affinity
Ionisation Energy and Electron Affinity : Chemical nature and reactivity of an element depend upon the ability of its atoms to donate or accept electrons. This can be measured quantitatively with the help of ionisation energy and electron affinity of its atoms : Ionisation energy : It is defined as the energy required to remove an electron completely from an isolated gaseous atom of an element. The energy required to remove the 1st electron is called first ionisation energy. A(g) + I . E1 → A+(g) + e–
Second Ionisation Energy : he energy required to remove an electron from a unipositive ion is called the second ionisation energy. A+(g) + I . E2 → A2+ (g) + e– The second ionisation energy is greater than the first ionisation energy due to increase in positive charge, hence increase in force of attraction between the nucleus and the valence electron. Ist I.E. < 2nd I.E. < 3rd I.E.