Explanation:
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Nobody knows this answer I checked a bunch of websites and they all don't know the answer.
The differences are <u>the number of neutrons</u> and the <u>atomic mass</u><u /><u />.
Copper-63 has an atomic mass of 63 amu, and has 34 neutrons.
Copper-65 has an atomic mass of 65 amu, and has 36 neutrons.