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Language of Chemistry — CHEMISTRY STD 8 — Question

ICSE BoardEnglish MediumSTD 8CHEMISTRYLanguage of Chemistry3 Marks
Question
Explain the term 'variable valency' Copper having electronic configuration $2,8,18,1$ exhibits variable valency. Give a reason for the same $\&$ name the compound $\ce{CuCl \& CuCl _2}$.
✓

Answer

Variable valency: "When an element has more than one valency, its valency is called variable valency." Copper exhibit valency ' $1$ ' and ' $2$ ' i.e. has variable valency reason for variable valency Valency is $-$ the number of electrons lost or gained from the outer shell of an atom of an element $-$ during chemical reaction. Variation in this gain or loss results in 'variable valency'.
Lower valency ends with $- ous$
Higher valency ends with $- ic$
$\ce{CuCl}$ is named as cuprous chloride $($lower valency$)$
OR
$\ce{Cu [ I ] Cl}$ i.e. Copper $\ce{[I]}$ chloride and
$\ce{CuCl _2-}$ Cupric chloride $($higher valency$)$
i. e. Copper $\ce{[II]}$ chloride $\ce{Cu [ II ] Cl _2}$

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