Question

Electronic configuration of copper can be represented as

• A. $[\mathrm{Ar}]\,4s^1\,3d^{10}$
• B. $[\mathrm{Ar}]\,4s^2\,3d^9$
• C. $[\mathrm{Ar}]\,4s^2\,3d^9\,4p^1$
• D. $[\mathrm{Ar}]\,4s^2\,3d^{10}\,4p^1$

Hint:

Copper and chromium are important exceptions to the Aufbau principle because half-filled and completely filled \(d\)-orbitals are especially stable.

Answer 1

The Correct Option is A

Concept: The electronic configuration of an atom is obtained by filling electrons according to the Aufbau principle. However, copper is an exception because a completely filled \(3d\)-subshell is more stable than a partially filled one. Copper has atomic number \[ Z=29 \] which means it contains \(29\) electrons.

Step 1: Write the expected electronic configuration. According to the normal filling order, \[ \mathrm{Cu}=[\mathrm{Ar}]\,4s^2\,3d^9 \]

Step 2: Apply the stability rule. A completely filled \(d\)-subshell possesses extra stability because of symmetrical electron distribution. Therefore, one electron from the \(4s\) orbital shifts to the \(3d\) orbital: \[ [\mathrm{Ar}]\,4s^2\,3d^9 \longrightarrow [\mathrm{Ar}]\,4s^1\,3d^{10} \]

Step 3: Identify the correct option. The configuration \[ [\mathrm{Ar}]\,4s^1\,3d^{10} \] matches option (A). center minipage0.45

Electronic configuration of Cu = $[\mathrm{Ar}]\,4s^1\,3d^{10}$ minipage center