The alkali metals

Options

A. form salt-like hydrides
B. form predominantly covalent salts
C. show decreased chemical reactivity with oxygen in going from Li to Cs
D. show increasing electronegativity form Li to Cs.

Explanation

### Step-by-Step Solution:

1. **Understanding Alkali Metals**:
- Alkali metals are the elements found in Group 1 of the periodic table. This group includes lithium (Li), sodium (Na), potassium (K), rubidium (Rb), and cesium (Cs).

2. **Analyzing the Options**:
- We have four statements regarding alkali metals, and we need to determine which one is correct.

3. **Option A: Forms Salt-like Hydrides**:
- Alkali metals react with hydrogen to form hydrides. For example, sodium reacts with hydrogen to form sodium hydride (NaH), which is ionic in nature and behaves like a salt.
- **Conclusion**: This statement is correct.

4. **Option B: Form Predominantly Covalent Salts**:
- Alkali metals are known to form ionic compounds rather than covalent ones. Common examples include sodium chloride (NaCl) and potassium hydroxide (KOH), which are ionic salts.
- **Conclusion**: This statement is incorrect.

5. **Option C: Show Decreased Chemical Reactivity with Oxygen from Lithium to Cesium**:
- The reactivity of alkali metals with oxygen actually increases as we move down the group. Lithium forms an oxide, while sodium forms a peroxide, and potassium forms a superoxide. Thus, reactivity increases down the group.
- **Conclusion**: This statement is incorrect.

6. **Option D: Show Increasing Electronegativity from Lithium to Cesium**:
- Electronegativity decreases as we move down the group from lithium to cesium. Therefore, this statement is also incorrect.
- **Conclusion**: This statement is incorrect.

7. **Final Answer**:
- The only correct statement is Option A: Alkali metals form salt-like hydrides.