What is Electropositivity?
Electropositivity can be defined as the tendency of an atom to donate electrons and form positively charged cations. This property is primarily exhibited by metallic elements, especially the alkali metals and the alkaline earth metals. It is important to note that electropositivity is the opposite of electronegativity, which is a measure of the tendency of an atom to gain electrons and form negatively charged anions. Therefore, highly electropositive elements have very low electronegativities and highly electronegative elements have very low electropositivity (electronegative elements typically do not have the tendency to lose electrons to form cations and electropositive elements generally do not to gain electrons to form anions).
Electropositive elements often form ionic salts with electronegative elements. For example, sodium is a highly electropositive element which readily gives up an electron in order to obtain a stable electronic configuration. Chlorine, on the other hand, is a highly electronegative element which readily accepts an electron to achieve a stable octet. Thus, sodium and chlorine can form an ionic bond with each other to yield sodium chloride (an ionic salt with the chemical formula NaCl).
Periodic Trends in the Electropositivity of Elements
The electropositivity of an element is dependent on several factors such as the metallic character of the element, the distance between the nucleus and the valence shell, the effective nuclear charge acting on the valence electrons, and the ionization energy of the element.
The periodic trends in the electropositivity exhibited by elements are always opposite to the periodic trends in the electronegativities of elements. Since electronegativity increases across a period, electropositivity decreases across periods. Similarly, since electronegativity decreases down a group, electropositivity increases while traversing down a group. Therefore, the elements at the top-right of the periodic table are the least electropositive and the elements at the bottom-left of the periodic table are the most electropositive.
Since electropositivity is primary a metallic attribute, it is dependent on the metallic character of the element. This is the reason why the alkali metals are regarded as the most electropositive elements (with caesium and francium being the most electropositive elements in the entire periodic table). Since fluorine, oxygen, and chlorine are the most electronegative elements in the periodic table, they are also the least electropositive elements.
Frequently Asked Questions on Electropositivity
Which is the most electropositive element?
Among all the elements of the periodic table, the alkali metals are considered to be the most electropositive. Caesium is known to be the most electropositive stable element. Though unstable, Francium is believed to be the most electropositive element in theory. Electropositivity is known to increase down groups and decrease across periods in the modern periodic table (i.e., electropositivity decreases from left to right and it increases from up to down).
What is the difference between electronegativity and electropositivity?
Electronegativity is the tendency of an atom to attract, in its combined state, a shared pair of bonded electrons. Non-metals are generally known to have high electronegativities (in comparison with metallic elements). Electropositivity is the tendency of an atom to donate electrons and withdraw form covalent bonds to form positively charged cations. Metallic elements are usually known to exhibit electropositivity.
Which is the least electropositive element?
Since fluorine is the most electronegative element in the entire periodic table. Therefore, it is the least electropositive element (since it has the lowest tendency to donate an electron and form a cation).
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