The alkali metals

Options

A. form salt like ionic hybrides
B. posses low ionisation potential
C. have high affinity for non-metals
D. have low density

Answer

To answer the question about alkali metals, we will analyze each of the provided statements and determine their validity step by step.

### Step-by-Step Solution:

1. **Identify the Alkali Metals:**
- The alkali metals include Lithium (Li), Sodium (Na), Potassium (K), Rubidium (Rb), Cesium (Cs), and Francium (Fr).
- **Hint:** Remember that alkali metals are found in Group 1 of the periodic table.

2. **Evaluate the First Statement (Ionic Hydrides Formation):**
- Alkali metals react with dihydrogen (H₂) to form hydrides (MH), which are ionic in nature.
- These hydrides are typically solid at room temperature and have high melting points.
- **Conclusion:** This statement is correct.
- **Hint:** Recall that ionic compounds generally form between metals and non-metals.

3. **Evaluate the Second Statement (Low Ionization Potential):**
- Alkali metals have low ionization energies, which decrease as you move down the group from Li to Cs.
- This low ionization potential allows them to easily lose their outermost electron.
- **Conclusion:** This statement is correct.
- **Hint:** Ionization energy is the energy required to remove an electron from an atom.

4. **Evaluate the Third Statement (High Affinity for Non-Metals):**
- Alkali metals have a strong tendency to lose their single outer electron to form M⁺ ions, which allows them to bond with non-metals.
- Their electronic configuration (ns¹) facilitates this process.
- **Conclusion:** This statement is correct.
- **Hint:** Consider how metals typically react with non-metals to form ionic compounds.

5. **Evaluate the Fourth Statement (Low Density):**
- Alkali metals are characterized by low density due to their large atomic size.
- As you move down the group, the size increases, which leads to a decrease in density.
- **Conclusion:** This statement is correct.
- **Hint:** Density is mass divided by volume; larger volume with similar mass results in lower density.

### Final Conclusion:
All four statements regarding alkali metals are correct.

### Summary:
- **Statement 1:** Correct (Ionic hydrides formation)
- **Statement 2:** Correct (Low ionization potential)
- **Statement 3:** Correct (High affinity for non-metals)
- **Statement 4:** Correct (Low density)

Thus, we conclude that all options provided in the question are true regarding alkali metals.