The element with atomic number 54 is likely to have the outer shell configuration as an element with atomic number

Options

A. 12
B. 18
C. 27
D. 14

Answer

To determine the outer shell configuration of the element with atomic number 54, we will follow these steps:

### Step 1: Identify the element with atomic number 54
The element with atomic number 54 is Xenon (Xe).

### Step 2: Write the electronic configuration of Xenon
The electronic configuration of Xenon is:
\[ \text{Xe: } [Kr] 4d^{10} 5s^{2} 5p^{6} \]

### Step 3: Determine the outer shell configuration
The outer shell configuration of Xenon can be identified as:
\[ ns^{2} np^{6} \]
where \( n = 5 \) (for Xenon, which is in the 5th period).

### Step 4: Compare with the configurations of the given atomic numbers
Now, we will compare the outer shell configurations of the elements with the given atomic numbers (12, 18, 27, 14).

1. **Atomic number 12 (Magnesium)**:
- Configuration: \[ 1s^{2} 2s^{2} 2p^{6} 3s^{2} \]
- Outer shell configuration: \( 3s^{2} \) (not noble gas configuration)

2. **Atomic number 18 (Argon)**:
- Configuration: \[ 1s^{2} 2s^{2} 2p^{6} 3s^{2} 3p^{6} \]
- Outer shell configuration: \( 3s^{2} 3p^{6} \) (noble gas configuration)

3. **Atomic number 27 (Cobalt)**:
- Configuration: \[ [Ar] 3d^{10} 4s^{2} \]
- Outer shell configuration: \( 4s^{2} \) (not noble gas configuration)

4. **Atomic number 14 (Silicon)**:
- Configuration: \[ 1s^{2} 2s^{2} 2p^{6} 3s^{2} 3p^{2} \]
- Outer shell configuration: \( 3s^{2} 3p^{2} \) (not noble gas configuration)

### Step 5: Conclusion
From the comparison, the only element that has a noble gas outer shell configuration similar to Xenon (which is \( ns^{2} np^{6} \)) is the element with atomic number 18 (Argon).

Thus, the element with atomic number 54 is likely to have the outer shell configuration as an element with atomic number **18**.