The quantum numbers for the outer electrons of an atom are given by
`n = 2, l = 0, m = 0, s = +1//2`

Options

A. Lithium
B. Beryllium
C. Hydrogen
D. Boron

Explanation

To determine which atom corresponds to the given quantum numbers \( n = 2, l = 0, m = 0, s = +\frac{1}{2} \), we can follow these steps:

### Step 1: Identify the Principal Quantum Number (n)
The principal quantum number \( n \) indicates the energy level of the electron. In this case, \( n = 2 \) means the electron is in the second energy level.

**Hint:** The principal quantum number \( n \) tells you the shell in which the electron resides.

### Step 2: Identify the Azimuthal Quantum Number (l)
The azimuthal quantum number \( l \) defines the subshell. Here, \( l = 0 \) corresponds to the s subshell.

**Hint:** The value of \( l \) determines the shape of the orbital: \( l = 0 \) for s, \( l = 1 \) for p, \( l = 2 \) for d, and so on.

### Step 3: Identify the Magnetic Quantum Number (m)
The magnetic quantum number \( m \) specifies the orientation of the orbital. Since \( m = 0 \) and \( l = 0 \), it indicates that we are dealing with the only orientation of the s orbital.

**Hint:** For \( l = 0 \), the only possible value for \( m \) is also 0.

### Step 4: Identify the Spin Quantum Number (s)
The spin quantum number \( s \) represents the spin of the electron. Here, \( s = +\frac{1}{2} \) indicates that the electron has an upward spin.

**Hint:** The spin quantum number can be either \( +\frac{1}{2} \) or \( -\frac{1}{2} \), representing the two possible spin states of an electron.

### Step 5: Determine the Electron Configuration
Given the quantum numbers, we can deduce that there is one electron in the 2s orbital. The electron configuration for the atom can be written as:
- \( 1s^2 \) for the first energy level (2 electrons)
- \( 2s^1 \) for the second energy level (1 electron)

Thus, the complete electron configuration is \( 1s^2 2s^1 \).

### Step 6: Identify the Atom
Now, we can count the total number of electrons:
- From \( 1s^2 \): 2 electrons
- From \( 2s^1 \): 1 electron
- Total = 2 + 1 = 3 electrons

The atomic number of the atom is 3, which corresponds to Lithium (Li).

**Final Answer:** The atom represented by the quantum numbers \( n = 2, l = 0, m = 0, s = +\frac{1}{2} \) is Lithium (Li).

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