Why is nh3 classified as a polar molecule

Explanation:

An ammonia molecule contains electronegative nitrogen atom. The difference between electronegativity of nitrogen and hydrogen atom is high.

Therefore, nitrogen will attract the shared pair of electrons more towards itself. As a result, there will be partial positive charge on hydrogen and partial negative charge on nitrogen.

Thus, due to these charges  is polar in nature.

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.