8. The compound 1,2-diaminoethane, HNCHCH, NH,, is a bidentate ligand; in formulae, it is usually abbreviated to ‘en'.
When 1,2-diaminoethane is added to [Co(NH)]* in aqueous solution,
[Co(en)3]2+ is formed. What is the best explanation for this?

answer: atomic mass was originally used to arrange elements on the periodic table, but is no longer used to organize the modern version.

explanation:

originally atomic mass was used to arrange elements on the periodic table from left to right in a row. each column then shows similar properties of elements of a group.

in modern periodic table, the atoms are arranged in increasing atomic number. as atomic number represents the number of protons in an atom which is unique for every atom.