Do all metals posses a closed packed structure?

Explanation

To determine whether all metals possess a closed packed structure, we need to analyze the concept of packing fraction and the types of crystal structures that metals can adopt.

### Step-by-Step Solution:

1. **Understanding Closed Packed Structures**:
Closed packed structures are arrangements of atoms in a crystal where the atoms are packed closely together. The two most common types of closed packed structures are Hexagonal Close Packed (HCP) and Cubic Close Packed (CCP).

2. **Defining Packing Fraction**:
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