Name one of the Halogens. What is the Name of the Element and its Chemical Symbol? What is the Atomic #? The Mass #? How many Protons, Neutrons, and Electrons (Total)
does it have? How many Shells does it have (what Period is it in)? How many Valence
Electrons does it have (what Valence Group is it in)?

answer: lol

explanation:

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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.