What is the formula for the ion which has 17 protons and 18 electrons?

Options

A. Cl
B. `Cl^(-)`
C. `Ar^(+)`
D. `Ar^(-)`

Explanation

To determine the formula for the ion with 17 protons and 18 electrons, we can follow these steps:

### Step 1: Identify the Element
The number of protons in an atom is equal to its atomic number. Since the ion has 17 protons, we can identify the element by looking up its atomic number.

**Hint:** The atomic number corresponds to the number of protons in an atom.

### Step 2: Find the Element with Atomic Number 17
The element with atomic number 17 is Chlorine (Cl).

**Hint:** Use the periodic table to find the element corresponding to the atomic number.

### Step 3: Determine the Charge of the Ion
In a neutral atom, the number of protons equals the number of electrons. Since this ion has 17 protons and 18 electrons, it has gained one extra electron.

**Hint:** Compare the number of protons and electrons to determine if the ion is positively or negatively charged.

### Step 4: Calculate the Charge
The charge of the ion can be calculated as follows:
- Protons = 17 (positive charge)
- Electrons = 18 (negative charge)

The overall charge of the ion is:
\[ \text{Charge} = \text{Number of Protons} - \text{Number of Electrons} = 17 - 18 = -1 \]

**Hint:** A negative charge indicates that the ion is an anion.

### Step 5: Write the Formula for the Ion
Since the ion has a charge of -1 and is derived from Chlorine, we can denote it as:
\[ \text{Cl}^- \]

**Hint:** The superscript indicates the charge of the ion.

### Final Answer
The formula for the ion with 17 protons and 18 electrons is:
\[ \text{Cl}^- \]