Question

q3. most copper atoms (~70%) are cu - 63. based on the atomic mass listed on the periodic table, what is the other stable isotope of copper found on earth? (there are another 27 isotopes known but these are radioactive = unstable).

Explanation:

The atomic mass of copper on the periodic table is approximately 63.55. Since about 70% is Cu - 63, to account for the atomic mass, the other stable isotope is Cu - 65. This is because the weighted - average of the masses of the two stable isotopes gives the atomic mass value on the periodic table.

Answer:

Cu - 65