The maximum number of the electrons which are permitted to be assigned to an energy shell of an atom is called the electron capacity of that shell. The distribution of electrons in different orbits or shells is governed by a scheme known as Bohr-Bury scheme. Electrons are filled in the shells in a stepwise manner in increasing order of energy of the energy shell.
Which of the following have same valency A(2,8, 2), B(2, 8, 4), C(2, 2), D(2,8)?

Options

A. A and B
B. B and C
C. A and C
D. C and D

Explanation

To determine which of the given elements (A, B, C, D) have the same valency based on their electronic configurations, we can follow these steps:

### Step 1: Identify the Valence Electrons
The first step is to identify the number of valence electrons for each element based on their electronic configurations.

- **Element A (2, 8, 2)**:
- The outermost shell (M shell) has 2 electrons.
- **Valence Electrons = 2**

- **Element B (2, 8, 4)**:
- The outermost shell (M shell) has 4 electrons.
- **Valence Electrons = 4**

- **Element C (2, 2)**:
- The outermost shell (L shell) has 2 electrons.
- **Valence Electrons = 2**

- **Element D (2, 8)**:
- The outermost shell (L shell) has no electrons (0).
- **Valence Electrons = 0**

### Step 2: Determine the Valency
Valency is determined by the number of electrons in the outermost shell:

- For elements with less than 4 valence electrons, the valency is equal to the number of valence electrons.
- For elements with more than 4 valence electrons, the valency is calculated as \(8 - \text{valence electrons}\).

Now let's calculate the valency for each element:

- **Element A**:
- Valence Electrons = 2
- **Valency = 2**

- **Element B**:
- Valence Electrons = 4
- **Valency = 4**

- **Element C**:
- Valence Electrons = 2
- **Valency = 2**

- **Element D**:
- Valence Electrons = 0
- **Valency = 0**

### Step 3: Compare Valencies
Now we compare the valencies of the elements:

- Element A: Valency = 2
- Element B: Valency = 4
- Element C: Valency = 2
- Element D: Valency = 0

### Conclusion
Elements A and C have the same valency of 2.

### Final Answer
**Elements A and C have the same valency.**

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