What are rare earths ?

Explanation

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

1. **Definition of Rare Earths**: Rare earths refer to a group of 17 chemical elements in the periodic table, specifically the lanthanides and scandium and yttrium, which are often found in the same ore deposits.

2. **Lanthanides**: The lanthanides are a series of 15 elements from lanthanum (La) to lutetium (Lu) in the periodic table. They are known as the 4f block elements due to their electron configuration.

3. **Occurrence**: Rare earth elements are not found in their free state in nature. Instead, they are typically found in various minerals and are extracted through mining and refining processes.

...