Which of the following statements regarding an orbital are correct

Options

A. An orbital is a definite trajectory around the nucleus in which electron can move
B. An orbital always has spherical trajectory
C. An orbital is the region around the nucleus where there si a 90-95% probability of finding all the electrons of an atom
D. An orbital is characterized by 3 quantum numbers n, l and m

Answer

To determine which statements regarding an orbital are correct, we need to analyze each statement based on our understanding of atomic orbitals and the quantum mechanical model of the atom.

### Step-by-Step Solution:

1. **Understanding the Definition of an Orbital**:
- An orbital is defined as a wave function for an electron in an atom. It describes a region around the nucleus where there is a high probability of finding an electron. This probability is typically around 90-95%.

**Hint**: Remember that orbitals are not fixed paths like orbits; they represent regions of space.

2. **Identifying the Quantum Numbers**:
- Orbitals are characterized by three quantum numbers:
- **Principal Quantum Number (n)**: Indicates the energy level and size of the orbital.
- **Azimuthal Quantum Number (l)**: Indicates the shape of the orbital.
- **Magnetic Quantum Number (m)**: Indicates the orientation of the orbital in space.

**Hint**: The three quantum numbers provide essential information about the electron's state.

3. **Analyzing the Statements**:
- **Statement 1**: "An orbital is a definite trajectory around the nucleus in which an electron can move."
- This statement is **incorrect**. Orbitals do not represent definite paths but rather regions of high probability for finding electrons.

- **Statement 2**: "An orbital always has a spherical trajectory."
- This statement is **incorrect**. While some orbitals (like the s-orbital) are spherical, others (like p, d, and f orbitals) have different shapes.

- **Statement 3**: "An orbital is the region around the nucleus where there is a 90-95% probability of finding all the electrons of an atom."
- This statement is **correct**. It accurately describes the probabilistic nature of orbitals.

- **Statement 4**: "An orbital is characterized by three quantum numbers n, l, and m."
- This statement is **correct**. It correctly identifies the quantum numbers that define an orbital.

4. **Conclusion**:
- The correct statements regarding orbitals are:
- Statement 3: Correct
- Statement 4: Correct

### Final Answer:
The correct statements regarding an orbital are statements 3 and 4.

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