Question

Why are metals hard?

• A. They have free electrons
• B. They gain electrons easily
• C. They are held by weak forces
• D. All of the above

Answer 1

The correct option is A They have free electrons

Metal have lots of free electrons which create a huge electron pressure (on the order of 100,000 $atm$), so to crush them,pressures higher than their internal electron gas pressure is required; this is why they are hard. In fact, metals can be bend because they have missing atoms (dislocations) in their crystal structure.