The values of quantum numbers n, l and m for the fifth electron of boron is

Options

A. n=2, 1 = 1, m=-1
B. n=2, 1 = 0, m = -1
C. n = 2, 1 = 2, m = -1
D. n = 1, 1 = 2, m = -1

Answer

To find the values of quantum numbers \( n \), \( l \), and \( m \) for the fifth electron of boron, we can follow these steps:

### Step 1: Determine the Atomic Number of Boron
Boron has an atomic number of 5. This means it has 5 electrons.

### Step 2: Write the Electron Configuration
The electron configuration for boron (atomic number 5) can be written as:
- 1s² 2s² 2p¹

This indicates that:
- The first shell (n=1) has 2 electrons in the 1s orbital.
- The second shell (n=2) has 2 electrons in the 2s orbital and 1 electron in the 2p orbital.

### Step 3: Identify the Fifth Electron
The fifth electron of boron is the one that occupies the 2p orbital since the first four electrons fill the 1s and 2s orbitals.

### Step 4: Assign the Principal Quantum Number (n)
For the fifth electron in the 2p orbital:
- The principal quantum number \( n \) is 2 (since it is in the second shell).

### Step 5: Assign the Azimuthal Quantum Number (l)
The azimuthal quantum number \( l \) is determined by the type of orbital:
- For s orbitals, \( l = 0 \)
- For p orbitals, \( l = 1 \)
- Since the fifth electron is in a p orbital, \( l = 1 \).

### Step 6: Assign the Magnetic Quantum Number (m)
The magnetic quantum number \( m \) can take values from \(-l\) to \(+l\):
- For \( l = 1 \), \( m \) can be -1, 0, or +1.
- The fifth electron in the 2p orbital can be assigned \( m = -1 \) (as it is the first electron in the 2p subshell).

### Summary of Quantum Numbers
Thus, for the fifth electron of boron:
- \( n = 2 \)
- \( l = 1 \)
- \( m = -1 \)

### Final Answer
The values of quantum numbers for the fifth electron of boron are:
- \( n = 2 \)
- \( l = 1 \)
- \( m = -1 \)

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