Hydrogen combines directly with

Options

A. `Ca`
B. `Cu`
C. `Zn`
D. `Fe`

Answer

To solve the question of which element hydrogen combines directly with, we can follow these steps:

### Step 1: Understand the Reactivity of Metals
Hydrogen can combine with metals to form hydrides. The reactivity of metals varies, and it is important to know which metals can react with hydrogen.

**Hint:** Remember that more reactive metals tend to form hydrides more readily.

### Step 2: Identify the Metals in the Question
The metals given in the question are Calcium, Copper, Zinc, and Iron. We need to analyze their reactivity with hydrogen.

**Hint:** Consider the position of these metals in the reactivity series of metals.

### Step 3: Analyze Each Metal
- **Calcium (Ca)**: Calcium is an alkaline earth metal and is highly reactive. It readily reacts with hydrogen to form calcium hydride (CaH₂).
- **Copper (Cu)**: Copper is a transition metal and is much less reactive than calcium. It does not readily form a hydride with hydrogen.
- **Zinc (Zn)**: Zinc can react with hydrogen, but it is less reactive than calcium.
- **Iron (Fe)**: Iron can also react with hydrogen, but again, it is less reactive than calcium.

**Hint:** Focus on the metals that are known to form stable hydrides.

### Step 4: Determine the Most Reactive Metal
Among the metals listed, Calcium is the most reactive and can combine directly with hydrogen to form a hydride. The other metals (Copper, Zinc, Iron) do not react as readily with hydrogen.

**Hint:** Look for the metal that is known for its high reactivity in forming compounds with hydrogen.

### Step 5: Conclusion
Based on the analysis, the correct answer is Calcium, as it combines directly with hydrogen to form calcium hydride.

**Final Answer:** Calcium (Ca) is the element that hydrogen combines directly with.