…A… are formed when atoms of different elements combine in a …B… ratio. Here, A and B refer to — Mole Concept and Some Basic Concepts of Chemistry Chemistry Question

💡 Solution & Explanation

# Analysis of the Blanks **Understanding the statement:** "…A… are formed when atoms of different elements combine in a …B… ratio." **Step 1: Identify what A represents** When atoms of *different elements* combine, they form chemical substances. The most accurate term here is **compounds**. **Step 2: Identify what B represents** Compounds are characterized by atoms combining in a **definite** (or fixed/simple whole number) ratio. This is a fundamental principle—compounds always have consistent elemental composition. **Step 3: Verify the logic** - Water ($H_2O$) always has hydrogen and oxygen in a 2:1 ratio - Salt ($NaCl$) always has sodium and chlorine in a 1:1 ratio - This consistency defines a compound versus a mixture **Conclusion:** | Blank | Answer | Reason | |-------|--------|--------| | **A** | **Compounds** | Different elements → compounds (not mixtures or elements) | | **B** | **Definite** | Compounds have fixed atomic ratios (not variable) | **Why this is correct:** The definition of a chemical compound inherently requires both conditions—different elements AND a constant combining ratio. This distinguishes compounds from mixtures (variable ratios) and from pure elements.