Chemistry

7. The following are all lists of successive ionisation energies for different elements. In each case, decide which group of the Periodic Table the element is to be found in.
Explain your answer


i) 799 2420 3660 25000 32800
ii) 736 1450 7740 10500 13600 18000 21700 25600
iii) 1000 2260 3390 4540 6990 8490 27100 31700

i) Must be in Group 3 - because there is a large increase between the third and fourth ionisation energy
ii) Must be in Group 2 - because there is a large increase between the second and third ionisation energy
iii) Must be in Group 6 - because there is a large increase between the sixth and seventh ionisation energy

A large increase indicates that there has been a significant change in the factors that affect ionisation energy: distance from the nucleus, shielding and nuclear charge. Shielding and nuclear charge change relatively consistently, resulting in the slow rise of ionisation energy. The distance from the nucleus will suddenly increase when an electron from an initially inner shell starts being removed. This only happens when all the electron in the outer shell have been removed. So before the increase is the number of electrons in the outer shell, thus telling us the group of the element.