The electronic configuration, `1s^(2) 2s^(2) 2p^(6) 3s^(2) 3p^(6) 3d^(9)`, represents a

Options

A. Metal atom
B. Non-metal atom
C. Non-metallic anion
D. Metallic cation

Explanation

To determine what the electronic configuration `1s^(2) 2s^(2) 2p^(6) 3s^(2) 3p^(6) 3d^(9)` represents, we can follow these steps:

### Step 1: Identify the Total Number of Electrons
First, we need to calculate the total number of electrons represented by the given electronic configuration.

- `1s^(2)` contributes 2 electrons
- `2s^(2)` contributes 2 electrons
- `2p^(6)` contributes 6 electrons
- `3s^(2)` contributes 2 electrons
- `3p^(6)` contributes 6 electrons
- `3d^(9)` contributes 9 electrons

Now, adding these together:
\[ 2 + 2 + 6 + 2 + 6 + 9 = 27 \text{ electrons} \]

### Step 2: Determine the Element
The total number of electrons (27) corresponds to the atomic number of an element. The element with atomic number 27 is Cobalt (Co).

### Step 3: Identify the Type of Element
Cobalt is a transition metal. Transition metals are typically characterized by their ability to form variable oxidation states and colored compounds, and they often have metallic properties.

### Step 4: Determine the Ionization State
The configuration given is `3d^(9)`, which suggests that cobalt has lost some electrons. Since the configuration ends with `3d^(9)`, it indicates that cobalt may exist in a +2 oxidation state (Co²⁺) after losing 2 electrons from the 4s and 3d orbitals.

### Conclusion
Thus, the electronic configuration `1s^(2) 2s^(2) 2p^(6) 3s^(2) 3p^(6) 3d^(9)` represents a **metallic cation**, specifically the cobalt ion (Co²⁺).

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