The number of electrons plus neutrons in `._(19)^(40)K^(+)` is-

Options

A. 38
B. 59
C. 39
D. 40

Explanation

To solve the problem, we need to determine the number of electrons and neutrons in the ion \( _{19}^{40}K^{+} \) (potassium ion). Here are the steps to find the solution:

### Step 1: Identify the atomic number and mass number
- The atomic number (Z) is given as 19. This represents the number of protons in the potassium atom.
- The mass number (A) is given as 40. This represents the total number of protons and neutrons in the nucleus.

### Step 2: Calculate the number of protons
- The number of protons is equal to the atomic number, which is 19.

### Step 3: Determine the number of electrons
- In a neutral atom, the number of electrons equals the number of protons. However, since we have a \( K^{+} \) ion, it has lost one electron.
- Therefore, the number of electrons = number of protons - 1 = 19 - 1 = 18 electrons.

### Step 4: Calculate the number of neutrons
- The number of neutrons can be calculated using the formula:
\[ \text{Number of neutrons} = \text{Mass number} - \text{Atomic number} \]
- Substituting the values:
\[ \text{Number of neutrons} = 40 - 19 = 21 \]

### Step 5: Calculate the total number of electrons plus neutrons
- Now, we need to find the sum of the number of electrons and neutrons:
\[ \text{Total} = \text{Number of electrons} + \text{Number of neutrons} = 18 + 21 = 39 \]

### Final Answer
The number of electrons plus neutrons in \( _{19}^{40}K^{+} \) is **39**.

---