Among the following represetations of excited states of atoms which is impossible?

Options

A. `1s^(1)2s^(1)`
B. `[Ne]3s^(2)3p^(3)4s^(1)`
C. `1s^(2)2s^(2)2p^(4)3s^(2)`
D. `[Ne]3s^(2)3p^(6)4s^(3)3d^(2)`

Answer

To determine which representation of excited states of atoms is impossible, we need to analyze each given electronic configuration based on the principles of atomic structure, particularly the Pauli Exclusion Principle and the Aufbau Principle.

### Step-by-Step Solution:

1. **Understand the Ground and Excited States**:
- The ground state of an atom is the lowest energy configuration of its electrons. When an atom absorbs energy, one or more electrons can move to higher energy orbitals, creating an excited state.

2. **Analyze Each Configuration**:
- We will evaluate each given representation to see if it adheres to the rules of electron configuration.

3. **Configuration 1: 1s¹ 2s¹**:
- This configuration indicates one electron in the 1s orbital and one in the 2s orbital. This is possible as both orbitals can accommodate electrons. Therefore, this representation is valid.

4. **Configuration 2: Ne 3s² 3p³ 4s¹**:
- This configuration suggests that the neon atom has 2 electrons in the 3s orbital, 3 in the 3p orbital, and 1 in the 4s orbital. This is also possible, as the electrons can be excited from the 3p to the 4s orbital. Thus, this representation is valid.

5. **Configuration 3: 1s² 2s² 2p⁴ 3s²**:
- This configuration shows 2 electrons in the 1s, 2 in the 2s, 4 in the 2p, and 2 in the 3s orbital. This is also possible since the total number of electrons does not exceed the maximum allowed in each subshell. Thus, this representation is valid.

6. **Configuration 4: Ne 3s² 3p⁶ 4s³ 3d²**:
- This configuration indicates 3 electrons in the 4s orbital. According to the Pauli Exclusion Principle, each orbital can hold a maximum of 2 electrons with opposite spins. Therefore, having 3 electrons in the 4s orbital is impossible. This representation is invalid.

### Conclusion:
The impossible representation of excited states of atoms is **Ne 3s² 3p⁶ 4s³ 3d²**.