Can someone show, with the aid of a diagram, why some metals and compounds are brittle?

Question

anonymous · Answer

Brittle mean, they show shining when the are cut.
when they are cut, the electrons of metal atoms gets energy and go to excited state, when the come back (cause relaxation) then they emit energy in the form of light. that is brittleness

anonymous · Answer

Isn't that exited state? I was thought that brittleness was just small crystal lattices of a compound.

anonymous · Answer

brittleness means lightining or shining

anonymous · Answer

I searched it up and it says that brittleness means brittleness "firm but easily broken".