Electropositive and Electronegative Radicals
We know that all the compounds can be classified in two ways; inorganic and organic. The organic compounds are mainly composed of carbon atoms which are bonded with each other. They are covalent compounds which are formed by the equal sharing of electrons between bonded atoms. Other types of compounds are inorganic compounds.
These compounds are formed by the combination of two oppositely charged parts which are called as radicals. Radicals can be defined as one atom or group of atoms which carry positive or negative charge on them. They behave as a single unit in solid state or in dissolved state in a solution. On the basis of charges and number of atoms in the radicals, they can be classified in four types.
Simple radicals are composed of one atom while compound radicals are composed of more than one atom. For example: hydrogen radical (H+) is a simple radical while phosphate radical (PO43-) is a compound radical. On the basis of charges; radicals can be classified electropositive and electronegative radicals. An electropositive radical carries positive charge such as H+, K+, Na+, Cr3+, Al3+ etc. On the contrary, electronegative radical carries negative charge such as O2-, PO43- and F- etc.
We can see that the charges on the radicals can be 1, 2, 3 and so on. On the basis of number of charges on radicals, they can be classified as monovalent, divalent, trivalent, tetravalent and polyvalent. A monovalent radical has either 1+ or 1- charge such as H+, K+, Na+, F-. Similarly divalent radical carries 2 charge and trivalent 3+ or 3- charge on them like O2-, PO43- , As3+ and Au3+. Let’s see how a radical forms from a neutral atom. There are eleven electrons in a sodium atom. It has one electron in its valence shell.
Similarly chlorine has 17 electrons with 7 electrons in its valence shell. Sodium has to lose one electron to get octet configuration while Cl requires one electron to get octet configuration. Hence sodium will form sodium radical with 1+ charge on it and chlorine will form an electronegative radical (Cl1-). After such transfer of electrons from Na and Cl, they acquire positive and negative charge on them. Because of positive and negative charge on Na and Cl, they can attract each other through electrostatic force of attraction to form ionic compound.
Compared to covalent bonds, ionic or electrovalent bonds between electropositive and electronegative radicals are quite strong and difficult to break. They easily dissolve in water due to the formation of ions in the solution. The polar nature of radicals makes them soluble in polar solvents such as water.