The correct option is Gold.
Explanation
Malleability is a physical property of metals that defines their ability to be hammered, pressed, or rolled into thin sheets without breaking or cracking. This property is a result of the non-directional nature of metallic bonds, which allows layers of atoms to slide over one another when stress is applied.
Detailed Analysis:
- Gold (Au): Gold is the most malleable of all known metals. It can be beaten into extremely thin sheets, known as gold leaf, with a thickness of only a few hundred atoms. It is also the most ductile metal, meaning it can be drawn into the thinnest wires.
- Silver (Ag): Silver possesses high malleability and ductility, ranking second only to gold. While it can be formed into very thin sheets, it does not match the extreme malleability of gold.
- Copper (Cu): Copper is a malleable metal widely used in industrial applications. However, its capacity to be thinned without annealing is lower than that of gold or silver.
- Sodium (Na): Sodium is an alkali metal that is soft enough to be cut with a knife at room temperature. It does not exhibit the mechanical strength or crystal structure required to be hammered into sheets; instead, it deforms easily or reacts due to its high chemical reactivity.
Key Takeaway:
Gold holds the distinction of being both the most malleable and the most ductile metal, allowing it to be processed into foils thinner than paper.