Which source would be most reliable for gathering experimental results related to a new compound’s molecular mass?

a newspaper article that describes the compound's discovery
a scientific journal that provides the compound’s measurements
a television show that explains ways the compound can be used
a textbook that lists molecular masses of similar compounds

Explanation:

Atom:

It is a smallest particle of an element which may as may not have independent existence.  

The are very small in size.  

Their size is measured in unit nm (nanometer)  

1nm – 10⁻⁹ m.  

hydrogen atom is smallest of all size is only 10⁻¹⁰ nm  

Atoms are represented by symbols (given by berzelius )

Atomic mass of element-  

Active atomic mass of atom can’t be measured but relative atomic mass can be known.  

I.e.  relative atomic mass of an atom of element is defined as average relative mass of atom as compared with atom of 612c taken as 12u.

Atomic mass – no. Of times one atom of he element is heavier then 1/12th of c atom.  

Molecule

It  is smallest particle of an element or compound which is able to exist independently.  

Some element exist as  

Diatomic molecuel  eq:- O₂

Triatomic molecule  eq:- O₃

¬

So,  

Atomicity – is no. of atoms in a molecule of an element.  

Some more examples:- phosphorous  P4 (tetra atomic)  

   sulphur S8 (poly-atomic)  

   nitrogen N2 (diatomic)  

Molecular mass

It is the mass of molecule that is obtained by adding masses of atoms multiplied with number of atoms of each type .