Hydrogen forms compounds with elements having atomic numbers : 9,11,12, 17 and 20 . What are their chemical formulae ? Compare their chemical behaviour.

Explanation

To solve the question regarding the compounds formed by hydrogen with elements having atomic numbers 9, 11, 12, 17, and 20, we will first identify the elements and then write their respective chemical formulas. Finally, we will compare their chemical behavior.

### Step 1: Identify the Elements
- Atomic number 9: **Fluorine (F)**
- Atomic number 11: **Sodium (Na)**
- Atomic number 12: **Magnesium (Mg)**
- Atomic number 17: **Chlorine (Cl)**
- Atomic number 20: **Calcium (Ca)**
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