What is your definition/source for the most common elements? Like it is in the crust, in the surface of the Earth (crust+atmosphere), in the Earth as a whole, or in the universe? The answers contradict to what I would expect as a geochemist. Like much heavier elements such as gold and mercury would be much rare than lighter elements such as zirconium and scandium unless under special circumstances. Or is the common just meaning commonly used, or commonly known?