Why metals are highly reactive? Please, explain.
All metals are reactive by definition, but two groups are considered to be much more highly reactive than the rest. The Alkali Metals group consists of the first row on the left side of the periodic table - lithium, sodium, potassium, rubidium, cesium,and francium. These metals have just one electron in the outermost orbital, called a valence electron. They lose this electron very readily in reaction with other elements, becoming a +1 ion and releasing energy in the process; that's where the reaction comes from. A classic lab demonstration consists of putting a chunk of sodium into water, where it explodes violently. See the youtube link below for a demonstration of this - it's quite amazing!
The next column to the right, the Alkaline Earth Metals, consists of beryllium, magnesium, calcium, strontium, barium, and radium. These metals are not quite as reactive as the first group, but will still react- for instance, magnesium burns very readily. They have 2 valence electrons and will produce a +2 ion when reacting.
Metals are highly reactive as they want to complete octet in their outermost shell to acquire stability.
First, let's make clear the following fact: not all metals are highly reactive, but the metals that belong to the group 1, that are called alkali metals. The reactivity of these metals is very high under normal conditions.
The outer layers of alkali metals contain 1 electron that is quickly lost when reacting with other chemical compunds.
As well as there are metals that are highly reactive, in contrast, there are metals that are highly non-reactive, such as gold.