Electropositive Radicals with their Valency
We know that elements and compounds are pure substances. An element cannot be decomposed into simpler substances. They are listed in the periodic table. Each element can represent by elemental symbols such as Ca for calcium, N for nitrogen, K for potassium etc. Similarly a compound is considered to be a pure substance which can be further broken into simpler substances as it is composed of two or more elements.
Elements cannot be decomposed into any further simpler substances. In the elemental symbol, the 2nd letter in the symbol is a lower case letter such as ‘He’ for helium, ‘Ca’ for calcium, ‘Ne’ for neon. They can be in solid, liquid or gaseous state such as mercury (Hg), bromine (Br) and hydrogen (H). The charge on element forms electropositive or electronegative radicals. Radicals can be an atom or group of atom with some charge. A simple radical is composed of one atom while a compound radical is formed by the groups of atom. On the basis of charge on radical, they can be classified as electropositive and electronegative radicals.
An electropositive radical has positive charge while an electronegative radical has negative charge on it. The charge or valency of the radicals represents the combining capacity of the radicals. For example the valency of hydrogen atoms is one, it means that it can combine or displace one atom of the element and form a compound. Some common examples of it are hydrogen chloride [HCl], nitric acid [HNO3] and hydrofluoric acid [HF]. In sulphuric acid molecule, the valency of the sulphate radical is 2. Overall valency can be defined as the number of electrons which can donates or accepts by an atom to get the duplet state or octet state in its valence shell.
Valency of a radical is always a whole number. On the basis of valency, elements or radicals can be classified as monovalent (valency=1), divalent (valency=2), trivalent (valency=3) and so on. All metals form electropositive radicals while all non-metals form electronegative radicals
The charge on the radicals is due to lose or gain of electrons to get the stable valence shell configuration. The radicals with opposite charges attract each other to form electrovalent compounds which are also called as ionic compounds. The cation or electropositive radicals form ionic bond with electronegative radicals to form ionic compounds.
Since metals have tendency to lose electrons therefore they can easily form electropositive radicals such as Na+, Fe3+, Mn7+ etc. The charge on electropositive radicals depends on the valence shell configuration of elements. For example; alkali metals have one electron in their valence shell therefore they form 1+ ions while alkaline earth metals have 2 electrons in their valence shell and form M2+ radicals. The d-block elements can show variable valency due to incomplete d-orbitals.