Which of the following statement are correct ?

Options

A. The electronic configuration of Cr is `[Ar] 3d^(5) 4s^(1)` (Atomic No. of cr = 24)
B. The magnetic quantum number may have a negative value
C. In silver atom, 23 electrons a spin of one type and 24 of the opposite type (Atomic No. of Ag = 47)
D. The oxidation state of nitrogen in `HN_(3) " is " -3`

Answer

To determine which statements are correct regarding the electronic configuration and properties of atoms, we will analyze each statement step by step.

### Step 1: Electronic Configuration of Chromium
- **Statement**: The electronic configuration of chromium is given as Argon (Ar) 3d⁵ 4s¹.
- **Analysis**: The atomic number of chromium (Cr) is 24. The correct electronic configuration is indeed Ar 3d⁵ 4s¹. This is because chromium is an exception to the expected filling order due to stability reasons.
- **Conclusion**: This statement is **correct**.

### Step 2: Magnetic Quantum Number
- **Statement**: The magnetic quantum number can have a negative value.
- **Analysis**: The magnetic quantum number (mₗ) can take values from -l to +l, where l is the azimuthal quantum number. For example, if l = 3, mₗ can be -3, -2, -1, 0, 1, 2, 3.
- **Conclusion**: This statement is **correct**.

### Step 3: Electrons in Silver Atom
- **Statement**: In a silver atom, 23 electrons are of one type, and 24 are of the opposite type.
- **Analysis**: The atomic number of silver (Ag) is 47. Its electronic configuration is [Kr] 5s¹ 4d¹⁰. The statement seems to imply a misunderstanding of electron spin. In a neutral silver atom, there are 47 electrons, but the distribution of spins is not simply categorized as one type and opposite type. The correct interpretation is that there are paired and unpaired electrons, but the phrasing of this statement is misleading.
- **Conclusion**: This statement is **incorrect**.

### Step 4: Oxidation States
- **Statement**: If the oxidation state of nitrogen is -3, then hydrogen has a positive oxidation state.
- **Analysis**: In compounds, hydrogen typically has an oxidation state of +1. If nitrogen is -3, it indicates that nitrogen is gaining electrons, while hydrogen is losing them. Thus, the statement is logically consistent.
- **Conclusion**: This statement is **correct**.

### Summary of Correct Statements
1. The electronic configuration of chromium is correct.
2. The magnetic quantum number can have negative values.
3. The statement regarding silver is incorrect.
4. The statement about oxidation states is correct.

### Final Answer
- **Correct Statements**: 1, 2, and 4 are correct. Statement 3 is incorrect.