The carbon-nitrogen bond in formamide, HCONH2, has been shown to have a bond length that is in between a typical C-N single bond and a C=N double bond. Provide an explanation for this observation, using relevant chemical structures to support your explanation.

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.  

answermeridional ;