The ability of an element to participate in a chemical reaction is measured in form of its __________.
Answer: ionization energy
The ability of an element to participate in a chemical reaction is called the reactivity of an element. Elements with high electronegativity will be very reactive, as will elements with low ionization energy. Alkali metals, for example, are very reactive but there is difference between sodium and cesium. Cesium has lower ionization energy so it is very reactive.
A chemical bond forms when it is energetically favorable, i.e., when the energy of the bonded atoms is less than the energies of the separated atoms. Some of the types of tabulated data associated with chemical bonds are ionization energy, electron affinity and electronegativity.
The ionization energy is the energy required to remove an electron from its orbital around an atom to a point where it is no longer associated with that atom. The first ionization energy applies to the neutral atoms. It is a minimum for the alkali metals which have a single electron outside a closed shell. It generally increases across a row on the periodic maximum for the noble gases which have closed shells. The second, third, etc., ionization energy applies to the further removal of an electron from a singly, doubly, etc., charged ion. The ionization energy of an element increases as one moves across a period in the periodic table because the electrons are held tighter by the higher effective nuclear charge. The ionization energy of the elements increases as one moves up a given group because the electrons are held in lower-energy orbitals, closer to the nucleus and therefore are more tightly bound (harder to remove).