ICSE BoardEnglish MediumSTD 7CHEMISTRYUnit - 4.1 Atomic Structure2 Marks
Question
Give three examples of elements having variable valency.
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Answer
Valency: The combining capacity of an atom is known as its valency. The number of bonds that an atom can form as part of a compound is expressed by the valency of the element. Variable valency: $\rightarrow$ Some metals can lose different numbers of electrons to form ions with different charges, this is called variable valency. $\rightarrow$ In some cases, the metals can lose electrons from the inner shell of the atom. $\rightarrow$ If an element exhibit two different electropositive valences, then for lower valency, the suffix -onus is used. $\rightarrow$ For higher valency, the suffix - ic is used at the end of the metal name. $\rightarrow$ Copper can show two valency Cu+2andCu+1. $\rightarrow$ Cu+2 is called Cupric ion and Cu+1 is called Cuprous ion. $\rightarrow$ Iron(Fe) can also show +2and+3 oxidation states. $\rightarrow$ Mercury (Hg) can show +1 and +2 oxidation states. Hence the transition elements have variable valences. For example, Copper, Iron, and Mercury.
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