The number of valence electrons present in `Ca` atom

Options

A. 3
B. 2
C. 8
D. 6

Answer

To determine the number of valence electrons present in a calcium (Ca) atom, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Atomic Number of Calcium**:
Calcium has an atomic number of 20. This means it has 20 electrons in a neutral atom.

2. **Determine Electron Configuration**:
The electrons are arranged in shells around the nucleus. The shells are filled in the following order:
- K shell (1st shell) can hold a maximum of 2 electrons.
- L shell (2nd shell) can hold a maximum of 8 electrons.
- M shell (3rd shell) can hold a maximum of 18 electrons, but in this case, we will only fill 10 electrons because we only have 20 electrons in total.

3. **Fill the Electron Shells**:
- Fill the K shell: 2 electrons (K = 2)
- Fill the L shell: 8 electrons (L = 8)
- Fill the M shell: 10 electrons (M = 10)
- At this point, we have filled 2 + 8 + 10 = 20 electrons.

4. **Identify the Valence Shell**:
The outermost shell for calcium is the M shell. This is also referred to as the valence shell.

5. **Count the Valence Electrons**:
The M shell contains 2 electrons. Therefore, the number of valence electrons in a calcium atom is 2.

### Final Answer:
The number of valence electrons present in a calcium atom is **2**.

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