Answer to Question #37617 in Inorganic Chemistry for BillI have a quiz on the trends of the periodic table and I became confused by the trend in reactivity. I think that in the s block, reactivity decreases from left to right and increases from top to bottom. Also, I think that in the p block, reactivity decreases from top to bottom and increases from left to right. First of all, is this correct? Also, what is the trend in the d block (transition metals)? Reactivity depends on many properties of substance. The main properties are the stability of molecules or crystal lattice of this substance, the energies of ionization and electron affinities. Generally this properties change periodically, but there are many deviations from this simple principle. The most reactive are the elements close to inert gases. Alkaline metals can simply lose one electon as well as halogens can accept it to form the stable octet. The elements in the middle of periodical table generally have the lower reactivity. But, in a broad sense, you should talk about reactivity against another substance. For example oxygen and fluorine are strong and highly reactive oxidizers, however they do not interact with each other.