The atomic number of an element which can not show the oxidation state of `+3` is-

Options

A. 13
B. 32
C. 33
D. 17

Answer

To determine the atomic number of an element that cannot show an oxidation state of +3, we need to analyze the electronic configurations of elements and their ability to lose electrons.

### Step-by-Step Solution:

1. **Understanding Oxidation States**:
- Oxidation states represent the degree of oxidation of an atom in a compound. An oxidation state of +3 means that the element can lose three electrons.

2. **Identifying Elements with +3 Oxidation State**:
- Elements that can exhibit a +3 oxidation state typically have three or more valence electrons that can be lost. For example, elements in groups 13 (like Aluminum) can show +3 oxidation states.

3. **Finding Elements that Cannot Show +3 Oxidation State**:
- Elements that cannot show a +3 oxidation state either do not have enough valence electrons or have a stable electronic configuration that does not favor losing three electrons.

4. **Analyzing Specific Elements**:
- Let's consider some elements:
- **Aluminum (Atomic number 13)**: Configuration is [Ne]3s²3p¹; can lose 3 electrons.
- **Silicon (Atomic number 14)**: Configuration is [Ne]3s²3p²; can lose 4 electrons but can also show +3.
- **Phosphorus (Atomic number 15)**: Configuration is [Ne]3s²3p³; can show +3 oxidation state.
- **Chlorine (Atomic number 17)**: Configuration is [Ne]3s²3p⁵; can show +3 oxidation state.
- **Noble Gases (like Argon, Atomic number 18)**: Configuration is [Ne]3s²3p⁶; do not lose electrons and cannot show +3 oxidation state.

5. **Conclusion**:
- The element that cannot show a +3 oxidation state is Argon (atomic number 18) because it has a complete outer shell and does not lose electrons.

### Final Answer:
The atomic number of the element which cannot show the oxidation state of +3 is **18**.