The period number in the long form of the periodic table is equal to (A)Magnetic quantum number of any element of the period (B)Atomic number of any element of the period (C)Maximum principal quantum number of any element of the period (D)Maximum azimuthal quantum number of any element of the period

Options

A. Magnetic quantum number of any element of the period
B. Atomic number of any element of the period
C. Maximum principak quantum number of any element of the period
D. Maximum azimuthal quantum number of any element of the period

Answer

To determine the correct answer to the question regarding the period number in the long form of the periodic table, we need to analyze each option provided.

### Step-by-Step Solution:

1. **Understanding Period Number**: The period number in the periodic table corresponds to the highest principal quantum number (n) of the electrons in the outermost shell of an atom.

2. **Analyzing Option (A)**:
- **Magnetic Quantum Number (m)**: This quantum number indicates the orientation of the orbital and does not directly relate to the period number.
- **Conclusion**: This option is incorrect.

3. **Analyzing Option (B)**:
- **Atomic Number**: The atomic number indicates the total number of protons in an atom and does not correlate with the period number since multiple elements can share the same period but have different atomic numbers.
- **Conclusion**: This option is incorrect.

4. **Analyzing Option (C)**:
- **Maximum Principal Quantum Number (n)**: This represents the highest energy level that electrons occupy in an atom. For example, in the case of carbon (atomic number 6), the electronic configuration is 1s² 2s² 2p², where the highest principal quantum number is 2. Similarly, for chlorine (atomic number 17), the configuration is 1s² 2s² 2p⁶ 3s² 3p⁵, where the highest principal quantum number is 3.
- **Conclusion**: This option is correct as it directly relates to the period number.

5. **Analyzing Option (D)**:
- **Maximum Azimuthal Quantum Number (l)**: This quantum number indicates the shape of the orbital and is not directly related to the period number. It represents the subshells (s, p, d, f) but does not indicate the period.
- **Conclusion**: This option is incorrect.

### Final Answer:
The correct answer is **(C) Maximum principal quantum number of any element of the period**.

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