How many of the following show variable oxidation states in their compounds ?
`Sc, Cr, Cu, Zn, Fe, Hg, La`

Answer

To determine how many of the given elements show variable oxidation states in their compounds, we will analyze each element one by one.

1. **Scandium (Sc)**:
- Scandium primarily exhibits oxidation states of +2 and +3.
- **Variable oxidation states**: Yes (2 states).

2. **Chromium (Cr)**:
- Chromium can exhibit multiple oxidation states including +2, +3, +4, +5, and +6.
- **Variable oxidation states**: Yes (5 states).

3. **Copper (Cu)**:
- Copper shows oxidation states of +1 and +2.
- **Variable oxidation states**: Yes (2 states).

4. **Zinc (Zn)**:
- Zinc predominantly exhibits a single oxidation state of +2.
- **Variable oxidation states**: No (1 state).

5. **Iron (Fe)**:
- Iron can exhibit oxidation states of +2, +3, +4, +5, and +6.
- **Variable oxidation states**: Yes (5 states).

6. **Mercury (Hg)**:
- Mercury shows oxidation states of +1 and +2.
- **Variable oxidation states**: Yes (2 states).

7. **Lanthanum (La)**:
- Lanthanum primarily exhibits a single oxidation state of +3.
- **Variable oxidation states**: No (1 state).

Now, let's summarize the findings:

- **Elements with variable oxidation states**: Sc, Cr, Cu, Fe, Hg.
- **Elements without variable oxidation states**: Zn, La.

Counting the elements that show variable oxidation states:
- Sc (2 states)
- Cr (5 states)
- Cu (2 states)
- Fe (5 states)
- Hg (2 states)

Total = 5 elements (Sc, Cr, Cu, Fe, Hg).

**Final Answer**: 5 elements show variable oxidation states in their compounds.

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