The measure of the ability of the elements mainly metals to donate electrons for the formation of the positive ions is called electropositivity. On the other hand, the elements which can easily accept the electrons for the formation of negative ions are known as electronegative elements. Non-metals are examples of electronegative elements.
Electropositivity can be defined as the tendency of an atom to donate electrons to form positively charged cations. The property to form positively charged cations is most probably exhibited by the metallic elements in the periodic table, especially the alkali metals and the alkaline earth metals.
Electropositivity is just the opposite of electronegativity. The highly electronegative elements have very low electropositivity whereas the highly electropositive elements have very low electronegativity. The electronegative elements usually form ionic salts with the electronegative elements. Sodium which is a highly electropositive element gives up an electron to obtain a stable electronic configuration. On the other hand, chlorine is a highly electronegative element that accepts an electron to achieve a stable octet.
Therefore, the electropositive element sodium and the electronegative element chlorine can form an ionic bond with each other to give sodium chloride. Sodium chloride is also known as common salt which is consumed every day.
Periodic Trends in The Electropositivity of The Elements
The electropositivity of an element depends on various factors like the metallic character of an element, the ionization energy of an element, the distance between the nucleus and the valance shell, and also the effective nuclear charge acting on the valence shell. The periodic trends in electropositivity exhibited by the elements are always opposite to the periodic trends in the electronegativities of the elements.
Electronegativity of the elements increases across a period whereas the electropositivity of the elements decreases across the periods, the electronegativity of the elements decreases down the group, and the electropositivity of the elements increases while traversing down a group. This is the reason why the elements at the top right of the periodic table are the least electropositive and the elements to the bottom left of the periodic table are always electropositive.
The electropositivity is a metallic attribute; it is dependent on the metallic character of an element. This is the only reason why all the alkali metals are regarded as the most electropositive elements in the periodic table. Cesium and francium are the highest electropositive elements in the entire periodic table. Whereas, fluorine, chlorine, and oxygen are the most electronegative elements in the periodic table which also means that they are the least electropositive elements in the periodic table.
The tendency of an element to lose the electrons to form the positive ions is called the electropositive character. It is also called the metal character. The elements which have very low ionization energies have a higher tendency to lose the electrons and therefore they are electropositive or metallic in their behavior. The alkali metals are always the most highly electropositive elements.
The reactivity of the metal decreases from the left to the right in a period as the tendency of an element to lose electrons decreases.
The reactivity of the metals increases from the top to the bottom in a group because the tendency of an element to lose the electrons increases in a period.
In a periodic table, the electropositivity or the metallic characters increases from the top to the bottom of the group.
In a periodic table, the elements are usually divided into two groups. The first group of elements is called metals and the second group of the elements is known as the non-metals. The metals and the non-metals are also divided into two categories which include electropositive and electronegative.
The electropositive is those elements or groups that give up electrons i.e. metals and acidic hydrogen. Electro positive elements are those elements whose electrode potential is more positive than that of a standard hydrogen electrode which is assigned an arbitrary value of zero. Examples of univalent alkali metals are Li+, Na+, K+, etc. An example of divalent alkaline earth metals is Be2+, Mg2+, Ca2+.