efine the term ionization energy and electron affinity. exemplify how they show periodicity in elements
Ionization energy is the minimum amount of energy required to remove the most loosely bound electron of an isolated neutral gaseous atom or molecule.
The ionization energy always increases in the period when moving from alkali metals to inert gases.
Na:495,8 Mg:737,7 Al:577,6 Si:786,5 P:1011,8 S:999,6 C:l1251,2 Ar:1520,6 kJ/mol
Electron affinity is defined as the amount of energy released when an electron is attached to a neutral atom or molecule in the gaseous state to form a negative ion.
Electron affinity generally increases across a period (row) in the periodic table prior to reaching group 18. This is caused by the filling of the valence shell of the atom; a group 17 atom releases more energy than a group 1 atom on gaining an electron because it obtains a filled valence shell and therefore is more stable.