How many of the following clements exclusively occur in combined state? Gold, iron, zinc, aluminium, platinum, sodium, magnesium

Answer

To determine how many of the given elements exclusively occur in a combined state, we will analyze each element individually:

1. **Gold (Au)**: Gold is a noble metal and does not readily react with other elements. It is commonly found in its free (native) state.
- **Conclusion**: Gold does not occur in a combined state.

2. **Iron (Fe)**: Iron commonly exists in nature as iron oxide (e.g., hematite, Fe2O3) and other combined forms.
- **Conclusion**: Iron occurs in a combined state.

3. **Zinc (Zn)**: Zinc is typically found in nature as zinc carbonate (ZnCO3) or zinc oxide (ZnO).
- **Conclusion**: Zinc occurs in a combined state.

4. **Aluminium (Al)**: Aluminium is primarily found in bauxite (Al2O3·H2O) and other ores.
- **Conclusion**: Aluminium occurs in a combined state.

5. **Platinum (Pt)**: Platinum is another noble metal that is found in its free state and does not readily combine with other elements.
- **Conclusion**: Platinum does not occur in a combined state.

6. **Sodium (Na)**: Sodium is highly reactive and is found in nature primarily in the form of sodium chloride (NaCl) and other compounds.
- **Conclusion**: Sodium occurs in a combined state.

7. **Magnesium (Mg)**: Magnesium is found in nature as magnesium chloride (MgCl2) and other combined forms.
- **Conclusion**: Magnesium occurs in a combined state.

Now, let's summarize the findings:
- Elements that occur in a combined state: Iron, Zinc, Aluminium, Sodium, Magnesium.
- Elements that do not occur in a combined state: Gold, Platinum.

**Final Count**: There are 5 elements (Iron, Zinc, Aluminium, Sodium, Magnesium) that exclusively occur in a combined state.

**Answer**: 5