a subscript of a chemical formula is the number of atoms of the element.
chemical element is the generic terms of a kind of atom that with the same inuclear charge.
and atom is the smallest particles in chemical change.
chemical element is the general term for the same type of atoms; and atoms constitute the basic unit of element.
if a substance with different atoms in it.it is a compound.
if the density of the object is larger than the liquid's.it will sink.
the last question i can't understand whats your meaning.