The number of electrons in the atom of an element X is 18 and the number of neutrons is 22. Which of the following is the correct representation of an atom of this element?

Options

A. `""_(19)^(40)X`
B. `""_(18)^(22)X`
C. `""_(22)^(40)X`
D. `""_(18)^(40)X`

Explanation

To solve the question regarding the correct representation of an atom of element X with 18 electrons and 22 neutrons, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Number of Protons**:
- In a neutral atom, the number of protons is equal to the number of electrons. Given that element X has 18 electrons, it will also have 18 protons.
- **Protons = 18**

2. **Determine the Number of Neutrons**:
- The problem states that there are 22 neutrons.
- **Neutrons = 22**

3. **Calculate the Atomic Mass**:
- The atomic mass (A) of an element is the sum of the number of protons and neutrons.
- Atomic Mass (A) = Number of Protons + Number of Neutrons
- A = 18 (protons) + 22 (neutrons) = 40
- **Atomic Mass = 40**

4. **Determine the Atomic Number**:
- The atomic number (Z) is defined as the number of protons in the nucleus of an atom.
- Since we have 18 protons, the atomic number will also be 18.
- **Atomic Number = 18**

5. **Write the Correct Representation**:
- The standard representation of an element is written as:
\[ \text{Element Symbol} \quad \frac{A}{Z} \]
- For element X, the representation will be:
\[ \text{X} \quad \frac{40}{18} \]

### Final Representation:
The correct representation of the atom of element X is:
\[ \text{X} \quad \frac{40}{18} \]