Question

you may know that the diamond is hardest material and it is a non metal and similarly Mercury is a soft material and it is a metal . write down the question raised in your mind

Answer 1

diamond is why the hardest mineral though it is not a metal and metal mercury is so soft

Answer 2

It is said that metals are hard and non-metals are soft.
This statement raises the question: is the metal non-metal classification proper for classifying properties of substances?
I guess u get what I'm thinking. If u want, u can write it better.