If .a. is the number of electrons in a dispositive ion and it has three neutrons more than the number of protons, identify the atomic number and mass number.

Options

A. `a+2, a+5`
B. `a+2, 2a+7`
C. `a+5, 2a+7`
D. `a+5, 2a+5`

Explanation

To solve the problem, we need to identify the atomic number and mass number of a dipositive ion (X²⁺) that has three neutrons more than the number of protons. Let's break this down step by step.

### Step 1: Understand the Dipositive Ion
A dipositive ion (X²⁺) means that the atom has lost 2 electrons. If we denote the number of electrons in the neutral atom as A, then in the dipositive ion, the number of electrons will be:
\[ \text{Electrons in X²⁺} = A - 2 \]

### Step 2: Determine the Number of Protons
In a neutral atom, the number of protons is equal to the number of electrons. Therefore, for the neutral atom:
\[ \text{Number of Protons} = A \]

Since the dipositive ion has lost 2 electrons, the number of protons remains the same as in the neutral atom:
\[ \text{Number of Protons} = A \]

### Step 3: Relate Neutrons to Protons
According to the problem, the number of neutrons is three more than the number of protons. Therefore, we can express the number of neutrons (N) as:
\[ N = A + 3 \]

### Step 4: Calculate the Mass Number
The mass number (M) of an atom is the sum of the number of protons and neutrons. Thus, we can write:
\[ M = \text{Number of Protons} + \text{Number of Neutrons} \]
Substituting the values we have:
\[ M = A + (A + 3) \]
\[ M = 2A + 3 \]

### Step 5: Identify the Atomic Number
The atomic number (Z) is equal to the number of protons, which we have established as:
\[ Z = A \]

### Summary
- **Atomic Number (Z)**: A
- **Mass Number (M)**: \( 2A + 3 \)

### Final Answer
The atomic number is \( A \) and the mass number is \( 2A + 3 \).

---