A non-metal which is gas at room temperature

Options

A. carbon
B. silicon
C. hydrogen
D. phosphorus

Explanation

To find a non-metal that is a gas at room temperature, we can follow these steps:

### Step 1: Understand Non-Metals
Non-metals are elements that generally lack the characteristics of metals. They are typically non-lustrous (not shiny), non-sonorous (do not produce a deep sound), and poor conductors of heat and electricity.

**Hint:** Remember that non-metals can exist in different states: solid, liquid, or gas.

### Step 2: Identify the States of Non-Metals
Most non-metals are found in solid form at room temperature, while a few exist as liquids or gases. We need to focus on the gaseous state.

**Hint:** Think about common non-metals and their usual states at room temperature.

### Step 3: List Non-Metals
Some common non-metals include:
- Carbon (solid)
- Sulfur (solid)
- Phosphorus (solid)
- Bromine (liquid)
- Iodine (solid)

**Hint:** Exclude the non-metals that are solids or liquids from your list.

### Step 4: Identify Gaseous Non-Metals
Among the non-metals, the ones that are gases at room temperature include:
- Hydrogen (H2)
- Nitrogen (N2)
- Oxygen (O2)
- Fluorine (F2)
- Chlorine (Cl2)

**Hint:** Look for non-metals that are commonly known to be gases.

### Step 5: Choose the Most Common Example
Among the gaseous non-metals, hydrogen is the simplest and most commonly recognized non-metal gas at room temperature.

**Hint:** Consider which non-metal gas is often mentioned in basic chemistry discussions.

### Final Answer
The non-metal that is a gas at room temperature is **Hydrogen (H2)**.

---