Copper atom has completely filled d orbitals `(3d^(10))` in its ground state. How can we say that it is a transition element

Explanation

To determine why copper (Cu) is considered a transition element despite having a completely filled d orbital configuration (3d^10) in its ground state, we need to analyze the characteristics of transition elements and the behavior of copper in different oxidation states.

### Step-by-Step Solution:

1. **Understanding Transition Elements**:
- Transition elements are defined as elements that have partially filled d orbitals in their ground state or in their most stable oxidation states. This includes elements from groups 3 to 12 of the periodic table.

2. **Copper's Electron Configuration**:
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