Question

analysis and questions: 1. was the mass of 20 pennies equal to 20 times the mass of one penny? explain. 2. in what year(s) did the mass of pe change? how could you tell? 3. how can you explain the fact that there are different “isotopes” of pennium? 4. why is the element “pennium” a good analogy or model for actual element isotopes? in what ways is the analogy misleading or incorrect? 5. name at least one other familiar item that could serve as a model for isotopes. 6. why are the atomic masses for most elements not whole numbers? 7. how are the three isotopes of hydrogen (hydrogen - 1, hydrogen - 2, and hydrogen - 3) alike? how are they different? 8. copper has two isotopes, copper - 63, and copper - 65. the relative abundance of copper - 63 is 69.1% and copper - 65, 30.9%. calculate the average atomic mass of copper.

Explanation:

Step1: Recall average - atomic - mass formula

The formula for the average atomic mass of an element with two isotopes is $Average\ atomic\ mass=(mass_1\times abundance_1)+(mass_2\times abundance_2)$. Here, for copper, $mass_1 = 63$, $abundance_1=0.691$, $mass_2 = 65$, and $abundance_2 = 0.309$.

Step2: Calculate the contribution of copper - 63

The contribution of copper - 63 to the average atomic mass is $63\times0.691 = 43.533$.

Step3: Calculate the contribution of copper - 65

The contribution of copper - 65 to the average atomic mass is $65\times0.309=20.085$.

Step4: Find the average atomic mass of copper

Add the two contributions together: $43.533 + 20.085=63.618$.

Answer:

$63.618$