A piece of copper had mass 3.4 grams before a reaction and 1.79 grams after the reaction. How many moles of copper reacted? (HINT: 3.4g Cu – 1.79 g Cu = 1.61 g Cu used)

answersilicon (si); oxygen (o);

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.