Question

what is the valency of first twenty elements by using klmn formula .pls tell me as its my paper​

Answer 1

here is your answer mate :-

The term "valence" or "valency" is used in chemistry to describe the potential an element or molecule has to bond. Similar to oxidation number and formal charge of an ion, the valency of an atom or molecule can be described as how many hydrogen atoms it can bond with. Radicals are similar to polyatomic ions, only without a formal charge. They are groups of atoms that can readily react with other elements and compounds.

Use the Octet Rule

Determine the electrons in the outer shells of the elements in the radical. This can be determined by counting how many columns on the periodic table the element is from a noble gas. For example, the cyanide radical (CN) has four outer electrons for carbon and five outer electrons for nitrogen.

Combine the atoms with covalent bonds, so they share as many electrons as possible without exceeding eight electrons. For cyanide, both carbon and nitrogen can share three electrons each. When nitrogen adds these three electrons to its existing five, it has eight electrons, known as an octet. Carbon ends up with seven electrons.

Determine how many electrons would need to be added to the molecule to make an octet for all the elements. This number is the radical's valence. In the example, one electron would be needed to give carbon an octet. Therefore, the cyanide radical has a valence of one.

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