Active metal is defined as that which has low ionization energy , that is, that metal that tends to lose electrons easily to form cations 1 . This behavior is due to the disposition of its valence electrons and causes the active metals to react more strongly and quickly than other elements.
The active metals are in group IA (or group 1) of the periodic table, the first column on the left side, a group much better known as alkaline metals . These are:
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- Lithium (Li)
- Sodium (Na)
- Potassium (K)
- Rubidio (Rb)
- Cesio (Cs)
- Francio (Fr)
Hydrogen is in the top position of group IA but is not considered an active metal , although it shares many characteristics with them.
Group IA and group IIA of the periodic table (alkaline metals and alkaline earth metals respectively) form the so-called reactive metals, being the most reactive metals of all, and it is very common to talk about active metals and reactive metals in an indistinct manner. refer to both groups.
The elements of group IA, which is generally referred to specifically as active metals, have a single electron in its outermost orbital (a single valence electron) with a configuration of the ns1 type :
- Li [He] 2 s 1 Rb [Kr] 5 s 1
- Na [Ne] 3 s 1 Cs [Xe] 6 s 1
- K [Ar] 4 s 1 Fr [Rn] 7 s 1
Given the low electronic affinity of these elements and their low ionization energy, they tend to yield this electron rapidly forming a monopositive cation (type M + ).
For example, if we put metallic sodium in contact with water, a violent reaction takes place in which the sodium loses an electron to form the Na + cation; the water molecule breaks forming OH - and H + ; OH - together with Na + forms sodium hydroxide (known as caustic soda ) remaining in solution; the H + on the other hand forms gaseous hydrogen (H 2 ) accepting the electrons yielded by the sodium:
2Na (s) + 2H_ {O} (l) → 2Na <+> (aq) + 2OH <-> (aq) + H <2> (g)
As you descend through group IA, the electropositivity and reactivity increase. The first lithium ionization energy, which is the first in the group, is 520.2 kJ / mol, and that of Francio, which is the last, is only 380 kJ / mol.
The Francio, therefore, is the active metal of greater reactivity , although it is very unstable. Its half-life is only 22 minutes. The element immediately superior to the francium, cesium, would be the most reactive element with a stable cation.
The high reactivity makes it very difficult to find active metals in a pure state in a natural environment , as they react easily with water, oxygen and other substances in the air to form other compounds.
This characteristic forces the scientists who work with these elements to keep them in strictly controlled conditions and isolated with some inert substance for them. It is usual for some type of oily substance, usually mineral oils , to be used as an insulator, which prevents the passage of oxygen and water vapor from the air.
The high reactivity of the active metals makes them dangerous in their handling but also makes them very useful. The active metals are used in controlled chemical reactions for the manufacture of a wide variety of products that we can find in our daily lives.
For example, Lithium is used in the manufacture of batteries, known as Li-ion batteries (a type of battery or dry cell ), widely used in gadgets and personal technology.