The sum of all the quantum number of helium atom is

Options

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

Explanation

To find the sum of all the quantum numbers of a helium atom, we first need to determine the quantum numbers for its electrons. Helium has an atomic number of 2, meaning it has two electrons.

### Step 1: Determine the Electronic Configuration
- Helium's electronic configuration is \(1s^2\). This means both electrons are in the 1s orbital.

### Step 2: Identify the Quantum Numbers
For each electron in the helium atom, we need to identify the four quantum numbers:
1. **Principal Quantum Number (n)**: This indicates the energy level of the electron.
- For helium, both electrons are in the 1s orbital, so \(n = 1\).

2. **Azimuthal Quantum Number (l)**: This indicates the subshell.
- For the s subshell, \(l = 0\).

3. **Magnetic Quantum Number (m)**: This indicates the orientation of the orbital.
- For the s subshell, \(m = 0\).

4. **Spin Quantum Number (s)**: This indicates the spin of the electron.
- The first electron can have \(s = +\frac{1}{2}\) and the second electron \(s = -\frac{1}{2}\).

### Step 3: Calculate the Quantum Numbers for Each Electron
- For the **first electron**:
- \(n = 1\)
- \(l = 0\)
- \(m = 0\)
- \(s = +\frac{1}{2}\)

- For the **second electron**:
- \(n = 1\)
- \(l = 0\)
- \(m = 0\)
- \(s = -\frac{1}{2}\)

### Step 4: Sum the Quantum Numbers
Now, we will sum the quantum numbers for both electrons:
- For the first electron:
\[ n + l + m + s = 1 + 0 + 0 + \frac{1}{2} = 1.5 \]
- For the second electron:
\[ n + l + m + s = 1 + 0 + 0 - \frac{1}{2} = 0.5 \]

### Step 5: Total Sum of All Quantum Numbers
Now, we add the sums from both electrons:
\[ 1.5 + 0.5 = 2 \]

### Final Answer
The total sum of all the quantum numbers of the helium atom is **2**.