The mass of a substance is the mass per mole of its entities, where the term entities can describe

            The molar mass of a substance is the mass per mole of its entities, where the term entities can describe atoms, molecules, ions or formula units.

Explanation:

                  Molar mass is the mass of any compound divided by mole. Means, if any chemical is given a specific molar mass it means this mass is being given by 6.022 × 10²³ entities of that chemical.

                  The molar mass of any compound is calculated by adding up the atomic masses of all atoms present in that chemical.

Example:

Molar Mass of H₂ =  1.008 + 1.008  =  2.016 g/mol

Molar Mass of NaOH  =  23 + 16 + 1  =  40 g/mol

Molar Mass of HCl =  1 + 35.5  =  36.5 g/mol

"among the transition metal elements, manganese and zinc have a slight lowering of electronegativities. the reason behind this is that the nuclear charges of these elements are slightly weaker than the other transition metal elements due to the way their valence electrons are filled up. both manganese and zinc have their valence electrons filled up to the 4th shell with 1 pair of electrons (4s2) completely occupying it. although the electrons in the 3rd shell (3d) are yet to be paired since the outer most shell is filled up, the ability of the nucleus to attract electrons is lessened. hence,   the electronegativity (or the ability to attract electrons) is lessened."

b. accuracy of the data matters alot more than its number of digits, organization or amount of detail. quantitative observation is more accepted than the qualitative observation.