The definite combining capacity of the atoms of each element, wherein electrons are lost, gained or shared to make the octet of electrons present in the outermost shell, is defined as valency . (i) The electronic configuration of silicon [14] is 2, 8, 4. It has 4 electrons in its outermost shell. So, the valency of silicon = 8 – the number of electrons in the outermost shell = 8 - 4 = 4. Hence, valency of silicon = 4. (ii) The electronic configuration of oxygen [8] is 2, 6. It has 6 (more ... The valency of oxygen is typically -2, meaning it tends to gain two electrons to achieve a stable octet configuration. This valency influences compound formation by oxygen readily forming compounds with elements that can donate electrons, such as metals, resulting in stable ionic compounds like oxides. The valence is the combining capacity of an atom of a given element, determined by the number of hydrogen atoms that it combines with. In methane, carbon has a valence of 4; in ammonia, nitrogen has a valence of 3; in water, oxygen has a valence of 2; and in hydrogen chloride, chlorine has a valence of 1. Chlorine, as it has a valence of one, can be substituted for hydrogen in many compounds. Phosphorus has a valence 3 in phosphine (PH3) and a valence of 5 in phosphorus pentachloride (PCl5 ... The valency of oxygen is 2 because its outermost shell contains 6 electrons and it needs 2 more electrons to attain a stable electron configuration. In chemical reactions, oxygen atoms form chemical bonds with other elements by sharing or donating electrons to complete their electron shells.
