In nature, copper has two isotopes: Cu-63 and Cu-65 with abundance 69 % and 31% respectively. Calculate the average atomic mass of copper.

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If a hydrogen atom is neutral, it must also have  one electron. an oxygen atom (o) has an atomic number of eight (8). this means a neutral oxygen atom has eight protons and eight electrons. the element actium (ac) has an atomic number of 89, so it has 89 protons and 89 electrons in a neutral atom