There are two rows of inner transition elements in the periodic table each containing 14 elements.The reason for this may be

Options

A. f-orbital has seven values for magnetic quantum number,hence total electrons are 14
B. in the periodic table there is space to accommodate 14 electrons only
C. Only 28 inner transition elements have been discovered till date
D. 28 is the maximum number of elements that any block can accommodate.

Explanation

To understand why there are two rows of inner transition elements in the periodic table, each containing 14 elements, we can break down the explanation into several steps:

### Step-by-Step Solution:

1. **Definition of Inner Transition Elements**:
- Inner transition elements are those elements that are found in the f-block of the periodic table. They are divided into two series: the lanthanides and the actinides.

2. **Number of Elements in Each Series**:
- Each series consists of 14 elements. The lanthanides start from lanthanum (La) and go through to lutetium (Lu), while the actinides start from actinium (Ac) and go through to lawrencium (Lr).

3. **Electronic Configuration**:
- The general electronic configuration of the inner transition elements is given by:
- For lanthanides: [Xe] 6s² 4f¹⁴
- For actinides: [Rn] 7s² 5f¹⁴
- The last electron enters the f-subshell, which can hold a maximum of 14 electrons (due to the 7 f orbitals, each capable of holding 2 electrons).

4. **F Subshell Capacity**:
- The f subshell has 7 orbitals, and according to the Pauli Exclusion Principle, each orbital can hold 2 electrons (with opposite spins). Thus, the total number of electrons that can occupy the f subshell is 7 orbitals × 2 electrons/orbital = 14 electrons.

5. **Conclusion**:
- Therefore, since there are two series of inner transition elements (lanthanides and actinides), each containing 14 elements due to the capacity of the f subshell, there are a total of 14 + 14 = 28 inner transition elements in the periodic table.

### Final Answer:
The reason there are two rows of inner transition elements in the periodic table, each containing 14 elements, is that the f subshell can accommodate a maximum of 14 electrons, and there are two series: the lanthanides and the actinides.

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