Question

Why does copper exhibits 1 and 2 Valency ?​

Answer 1

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⚘Variable oxidation states are normally shown by the elements of the d-block and the f-block as they possess incompletely filled d and f orbitals.

⚘ As a result, the number of electrons that can participate in bond formation can vary.

⚘ Since copper also belongs to d block and have incomplete d orbital therefore it also exhibits variable oxidation state.

Answer 2

Answer:

due to Aufbau Principle,

which states that

electrons are added to orbitals as protons are added to an atom. ..means Electrons go into the subshell having the lowest possible energy

thus  4s orbital is filled before 3d orbital and hence,

Copper is one of the transition elements and thus exhibits variable oxidation states. It has two valencies: +1 and +2 and the corresponding atoms are termed as Cuperous (+1 valency) and Cupric (+2 valency).

eg :

cu ; 4s^1 3d^10 is its configuration