Magnesium chloride contains magnesium ions, \( \mathrm{Mg}^{2+} \), and chloride ions, \( \mathrm{Cl}^{-} \). i Explain why a magnesium ion is positively charged. ii Explain why a chloride ion has a single negative charge.

To explain the charges of magnesium ions and chloride ions, let's break down the concepts of ions and their charges. ### i. Why is a magnesium ion positively charged? 1. **Atomic Structure**: Magnesium (Mg) has an atomic number of 12, which means it has 12 protons in its nucleus and, in its neutral state, it also has 12 electrons orbiting around the nucleus. 2. **Electron Configuration**: The electron configuration of magnesium is \( 1s^2 2s^2 2p^6 3s^2 \). This shows that magnesium has two electrons in its outermost shell (the 3s subshell). 3. **Ion Formation**: To achieve a more stable electron configuration, magnesium tends to lose these two outermost electrons. By losing two electrons, magnesium achieves the electron configuration of neon, which is a noble gas and is more stable. 4. **Charge Calculation**: When magnesium loses two electrons, it has 12 protons (positive charges) and only 10 electrons (negative charges). The difference between the number of protons and electrons gives the magnesium ion a charge of \( +2 \): \[ \text{Charge of } \mathrm{Mg}^{2+} = \text{Number of protons} - \text{Number of electrons} = 12 - 10 = +2 \] ### ii. Why does a chloride ion have a single negative charge? 1. **Atomic Structure**: Chlorine (Cl) has an atomic number of 17, meaning it has 17 protons and, in its neutral state, also has 17 electrons. 2. **Electron Configuration**: The electron configuration of chlorine is \( 1s^2 2s^2 2p^6 3s^2 3p^5 \). This indicates that chlorine has seven electrons in its outermost shell (the 3s and 3p subshells). 3. **Ion Formation**: To achieve a stable electron configuration, chlorine tends to gain one additional electron. By gaining one electron, chlorine achieves the electron configuration of argon, which is also a noble gas and is more stable. 4. **Charge Calculation**: When chlorine gains one electron, it has 17 protons and 18 electrons. The difference between the number of protons and electrons gives the chloride ion a charge of \( -1 \): \[ \text{Charge of } \mathrm{Cl}^{-} = \text{Number of protons} - \text{Number of electrons} = 17 - 18 = -1 \] ### Summary - A magnesium ion (\( \mathrm{Mg}^{2+} \)) is positively charged because it loses two electrons, resulting in more protons than electrons. - A chloride ion (\( \mathrm{Cl}^{-} \)) has a single negative charge because it gains one electron, resulting in more electrons than protons.