The list in which metals are arranged vertically in the decreasing order of chemical reactivity is called the ____ series.

Explanation

**Step-by-Step Text Solution:**

1. **Understanding the Question**: The question asks for the name of a list where metals are arranged in order of their chemical reactivity, from most reactive to least reactive.

2. **Identifying the Concept**: The concept that describes the arrangement of metals based on their reactivity is known as the "reactivity series." This series helps in understanding how metals react with each other and with non-metals.

3. **Explaining the Reactivity Series**: The reactivity series is a list of metals arranged in decreasing order of their reactivity. For example, potassium is at the top of the series, indicating it is highly reactive, while gold is at the bottom, indicating it is less reactive.

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