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 elements 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 answer the question regarding why there are two rows of inner transition elements in the periodic table, each containing 14 elements, we can follow these steps:

### Step 1: Understand the F Block
The inner transition elements are located in the f block of the periodic table. This block consists of two series: the lanthanides and the actinides.

**Hint:** Recall that the f block is characterized by the filling of f orbitals.

### Step 2: Determine the Magnetic Quantum Number
The f orbital has an azimuthal quantum number (l) of 3. The magnetic quantum number (m_l) can take values from -l to +l, which gives us a total of 2l + 1 possible values.

**Calculation:**
- For l = 3, the values of m_l are: -3, -2, -1, 0, +1, +2, +3.
- This results in 7 possible values.

**Hint:** Remember the formula for calculating the number of orbitals: 2l + 1.

### Step 3: Calculate the Total Number of Electrons
Since each f orbital can hold 2 electrons (due to opposite spins), the total number of electrons that can occupy the f block is:
- Total electrons = Number of orbitals × 2 = 7 × 2 = 14.

**Hint:** Each orbital can hold a maximum of 2 electrons.

### Step 4: Identify the Number of Rows
There are two series of inner transition elements: the lanthanides (elements 57 to 71) and the actinides (elements 89 to 103). Each series corresponds to the filling of the f orbitals.

**Hint:** Consider how many series of f block elements exist in the periodic table.

### Step 5: Conclusion
Thus, the reason there are two rows of inner transition elements, each containing 14 elements, is that the f block can accommodate a total of 14 electrons due to the 7 orbitals available in the f subshell.

**Final Answer:** The correct reason is that the f orbital has seven values of the magnetic quantum number, allowing for a total of 14 electrons.