A list of metals arranged in order of their decreasing reactivity is known as the ____ of metals.

Explanation

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks for the term used to describe a list of metals arranged according to their reactivity.

2. **Identifying the Concept**: In chemistry, metals can be arranged based on how reactive they are with other substances. This arrangement helps in predicting how metals will react in various chemical reactions.

3. **Finding the Correct Term**: The specific term used to describe this arrangement is the "activity series of metals." This series ranks metals from most reactive to least reactive.

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