Are you ready to take this lesson's quiz? The questions below will help you find out. Make sure you understand why each correct answer is correct—if you don't, review that part of the lesson.
The mass number of an atom is equal to what?
- the number of protons
- the number of electrons
- the number of neutrons
- the number of protons and neutrons
The atomic number is equal to the number of protons in the nucleus.
The number of electrons in a neutral atom is equal to the number of protons.
The number of neutrons in the nucleus of an atom is equal to the mass number minus the atomic number.
The mass number is the number of protons and neutrons in the nucleus.
Which of the following indicates the number of protons?
- mass number
- atomic number
- atomic mass
- neutron number
The mass number equals the number of protons and neutrons in the nucleus.
The atomic number indicates the number of protons.
The atomic mass is essentially the same as the mass number.
The number of protons is NOT always equal to the number of neutrons. The number of neutrons is equal to the mass number minus the atomic number.
In a 5.0 g sample of copper, which isotope would you expect to find the most? Use the given data.
| Isotope | Percent Abundance | Mass of Isotope (amu) |
|---|---|---|
| Copper-63 | 69.15 | 62.93 |
| Copper-65 | 30.85 | 64.93 |
- copper - 63
- copper - 65
- copper - 64
- There is the same amount of each isotope.
Copper - 63 has the greater percentage abundance of the two isotopes.
Copper - 65 has the lower percentage abundance of the two isotopes.
This isotope is not listed on the table.
Copper - 63 has the greater percentage abundance of the two isotopes.
How are isotopes of the same element different? Select all that apply.
- They have different numbers of protons.
- They have different numbers of neutrons.
- They have different numbers of electrons.
- They have different masses.
Some of these are incorrect.
You missed some correct choices.
Great! You got them all
The element rubidium has two isotopes: Rb-85 and Rb-87.
Rb-85 has a mass of 84.9118 u and an abundance of 72.15%.
Rb-87 has a mass of 86.9022 and an abundance of 27.85%.
What is the weighted average atomic mass of rubidium?
- 85.47 u
- 85.91
- 86
- 84.91118
\(\text{Average Atomic Mass} =\) \( \left( \frac{72.15\%}{100} + 84.9118\ \text{u} \right)+\)\(\left( \frac{27.85\%}{100}+ 86.9022\ \text{u} \right)\)
This is the unweighted average of the atomic masses for these two isotopes.
This is the average of the mass numbers of these two isotopes.
This is the mass of the most abundant isotope.
Summary
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