Give the name of the alkali metal which is radioactive.

Explanation

To solve the question of identifying the radioactive alkali metal, we can follow these steps:

### Step 1: Understand the Alkali Metals
Alkali metals belong to Group 1 of the periodic table. They include lithium (Li), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), and francium (Fr).

**Hint:** Remember that alkali metals are characterized by having one electron in their outermost shell.

### Step 2: Identify Radioactive Elements
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