Find the number of electrons present in the last shell of the Calcium.

Options

A. 1
B. 2
C. 3
D. 4

Answer

To find the number of electrons present in the last shell of Calcium, we can follow these steps:

### Step 1: Determine the Atomic Number of Calcium
Calcium (Ca) has an atomic number of 20. This means it has 20 electrons in its neutral state.

### Step 2: Write the Electronic Configuration
To find the distribution of electrons in the shells, we write the electronic configuration of Calcium. The electronic configuration is as follows:
1. The first shell can hold a maximum of 2 electrons: 1s²
2. The second shell can hold a maximum of 8 electrons: 2s² 2p⁶
3. The third shell can hold a maximum of 18 electrons, but for Calcium, it will hold only 8 electrons: 3s² 3p⁶
4. The fourth shell starts to fill with electrons: 4s²

So, the complete electronic configuration of Calcium is:
1s² 2s² 2p⁶ 3s² 3p⁶ 4s²

### Step 3: Identify the Last Shell
The last shell (or valence shell) is the shell with the highest principal quantum number (n). In this case, the highest value of n is 4 (from 4s²).

### Step 4: Count the Electrons in the Last Shell
In the last shell (n=4), we have:
- 4s², which means there are 2 electrons in the last shell.

### Conclusion
Thus, the number of electrons present in the last shell of Calcium is **2**.