Helium is used to fill gas ballons instead of hydrogen because it is lighter and non-inflammable

Explanation

**Step-by-Step Solution:**

1. **Understanding the Gases**: Both helium and hydrogen are lighter than air, which allows them to rise when used in balloons. This is the first reason why they are both considered for balloon filling.

2. **Comparing Properties**: While both gases are lighter than air, they have different chemical properties. Hydrogen is highly flammable, meaning it can easily catch fire and explode when exposed to a flame or spark.

3. **Safety Considerations**: Due to hydrogen's flammability, using it in balloons poses a significant safety risk. If a hydrogen-filled balloon were to come into contact with a flame or spark, it could lead to an explosion.

4. **Helium's Advantages**: In contrast, helium is a noble gas that is non-flammable and does not support combustion. This makes it a much safer option for filling balloons.

5. **Conclusion**: Therefore, helium is preferred over hydrogen for filling gas balloons because it is lighter than air and, importantly, non-inflammable, making it a safer choice for use in various applications, including party balloons and scientific experiments.

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