Xenon and krypton is used in electric bulbs to slow down the __________ of tungsten.

Explanation

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks what Xenon and Krypton are used for in electric bulbs, specifically in relation to tungsten.

2. **Identifying the Role of Tungsten**: Tungsten is used as a filament in electric bulbs. It is known for its high melting point and ability to emit light when heated.

3. **Understanding Sublimation**: Sublimation is the process where a solid turns directly into a gas without becoming a liquid first. For tungsten, this occurs at high temperatures (around 550 degrees Celsius).

4. **Role of Inert Gases**: Xenon and Krypton are noble gases, which means they are chemically inert. This property is important because it means they do not react with tungsten.

5. **Purpose of Using Xenon and Krypton**: By filling electric bulbs with these inert gases, the rate at which tungsten sublimates (turns into gas) is slowed down. This helps prolong the life of the filament.

6. **Final Answer**: Therefore, the correct term to fill in the blank is "sublimation." The complete statement is: "Xenon and Krypton are used in electric bulbs to slow down the sublimation of tungsten."

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