The relative atomic mass of chlorine is 35.5 . What does this tell you about the
abundance of the two naturally occurring isotopes of chlorine?
Magnesium chloride contains magnesium ions, , and chloride ions, .
i Explain why a magnesium ion is positively charged.
ii Explain why a chloride ion has a single negative charge.

Ask by Conner Wagner. in South Africa

Jan 23,2025

Question

The relative atomic mass of chlorine is 35.5 . What does this tell you about the
abundance of the two naturally occurring isotopes of chlorine?
Magnesium chloride contains magnesium ions, , and chloride ions, .
i Explain why a magnesium ion is positively charged.
ii Explain why a chloride ion has a single negative charge.

Ask by Conner Wagner. in South Africa

Jan 23,2025

UpStudy AI · Accepted Answer

### 1. Relative Atomic Mass of Chlorine (35.5)

**Explanation:**
- **Isotopes of Chlorine:** Chlorine naturally occurs mainly in two isotopic forms:
  - **^35Cl:** Has an atomic mass of approximately 34.969 amu.
  - **^37Cl:** Has an atomic mass of approximately 36.966 amu.
  
- **Relative Atomic Mass Calculation:** The relative atomic mass of an element is the weighted average of the masses of its naturally occurring isotopes, based on their abundance.

$$
  \text{Relative Atomic Mass} = \frac{(\% \text{ abundance of } ^{35}\text{Cl} \times 34.969) + (\% \text{ abundance of } ^{37}\text{Cl} \times 36.966)}{100}
  $$
  
- **Given Relative Atomic Mass:** Chlorine's relative atomic mass is **35.5**. This value suggests that the abundances of the two isotopes are nearly equal but slightly favor the lighter isotope (^35Cl).

**Conclusion:**  
A relative atomic mass of 35.5 indicates that **^35Cl** is slightly more abundant than **^37Cl** in nature. Specifically, roughly **75.76%** of chlorine atoms are **^35Cl**, and **24.24%** are **^37Cl**, calculating based on the average:

$$
35.5 = (0.7576 \times 35) + (0.2424 \times 37) \approx 35.5
$$

### 2. Magnesium Chloride Ions

Magnesium chloride ($$ \mathrm{MgCl}_2 $$) dissociates into magnesium ions ($$ \mathrm{Mg}^{2+} $$) and chloride ions ($$ \mathrm{Cl}^{-} $$) in solution.

#### i. Why is a Magnesium Ion Positively Charged?

**Explanation:**
- **Electron Configuration of Magnesium (Mg):**
  - Atomic number: 12
  - Neutral atoms have 12 protons and 12 electrons.
  - Electron configuration: $$ 1s^2 2s^2 2p^6 3s^2 $$
  
- **Ion Formation:**
  - To achieve a stable electron configuration similar to the noble gas neon ($$ \text{Ne} $$), magnesium **loses two electrons** from its outermost energy level (3s orbital).
  
  $$
  \mathrm{Mg} \rightarrow \mathrm{Mg}^{2+} + 2e^-
  $$
  
- **Charge Result:**
  - Losing two electrons (each with a negative charge) results in a net positive charge of **+2**.

**Conclusion:**  
A magnesium ion is **positively charged** ($$ \mathrm{Mg}^{2+} $$) because the magnesium atom loses two electrons to achieve a stable electron configuration, resulting in a net positive charge.

#### ii. Why Does a Chloride Ion Have a Single Negative Charge?

**Explanation:**
- **Electron Configuration of Chlorine (Cl):**
  - Atomic number: 17
  - Neutral atoms have 17 protons and 17 electrons.
  - Electron configuration: $$ 1s^2 2s^2 2p^6 3s^2 3p^5 $$
  
- **Ion Formation:**
  - To achieve a stable electron configuration similar to the noble gas argon ($$ \text{Ar} $$), chlorine **gains one electron** to fill its 3p orbital.
  
  $$
  \mathrm{Cl} + e^- \rightarrow \mathrm{Cl}^-
  $$
  
- **Charge Result:**
  - Gaining one electron (each with a negative charge) results in a net negative charge of **-1**.

**Conclusion:**  
A chloride ion has a **single negative charge** ($$ \mathrm{Cl}^- $$) because the chlorine atom gains one electron to complete its valence shell, resulting in a net negative charge.
**Relative Atomic Mass of Chlorine (35.5):** - Chlorine has two main isotopes: **^35Cl** (75.76% abundance) and **^37Cl** (24.24% abundance). **Magnesium Chloride Ions:** - **Magnesium Ion ($$ \mathrm{Mg}^{2+} $$):** Positively charged because magnesium loses two electrons to achieve a stable electron configuration. - **Chloride Ion ($$ \mathrm{Cl}^- $$):** Negatively charged because chlorine gains one electron to achieve a stable electron configuration.

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