Physics 12 SMC H.-F. Lai Homework Solutions Ch. 10 Q2. The latest number is 115.
Atoms are the smallest units for chemical reactions.
An atom is the smallest unit of an element that has the element's chemical properties. A molecule is the smallest unit of any substance that has all the substance s chemical properties. Atoms combine to form molecules. There are only 115 distinct atoms, which combine to form a great variety of molecules. The standard atomic mass unit is amu .