If quantum number for last electron is `n=3,l=0,m=0`, then atomic number is

Options

A. 12,13
B. 13,14
C. 10,11
D. 11,12

Explanation

To determine the atomic number of the element with the given quantum numbers for the last electron, we can follow these steps:

### Step 1: Identify the Quantum Numbers
The quantum numbers provided are:
- Principal quantum number (n) = 3
- Azimuthal quantum number (l) = 0
- Magnetic quantum number (m) = 0

### Step 2: Determine the Orbital Type
The azimuthal quantum number (l) indicates the type of orbital:
- l = 0 corresponds to the s orbital.

Since n = 3 and l = 0, the last electron is in the 3s orbital.

### Step 3: Fill the Electron Configuration
To find the atomic number, we need to consider the electron configuration leading up to the 3s orbital. The filling order of orbitals is as follows:
1. 1s
2. 2s
3. 2p
4. 3s

The electron configuration is:
- 1s² (2 electrons)
- 2s² (2 electrons)
- 2p⁶ (6 electrons)
- 3s¹ (1 electron, since the last electron is in the 3s orbital)

### Step 4: Calculate the Total Number of Electrons
Now, we can add up the electrons:
- 1s²: 2 electrons
- 2s²: 2 electrons
- 2p⁶: 6 electrons
- 3s¹: 1 electron

Total = 2 + 2 + 6 + 1 = 11 electrons

### Step 5: Determine the Atomic Number
The atomic number (Z) of an element is equal to the number of electrons in a neutral atom. Therefore, the atomic number of the element is 11.

### Final Answer
The atomic number is **11**.

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