Test Your Knowledge
Key Idea 1: Isotopes
1) All atoms of carbon have 6 protons, carbon-12 has __ neutrons and carbon-13 has __neutrons.
- 12 and 13
- 18 and 19
- 6 and 7
- They both have 6
2) A sample of magnesium, which contains a mixture of isotopes of magnesium-24, magnesium-25, and magnesium-26 atoms is analyzed with a mass spectrometer. How many peaks do you expect to see in the mass spectrum?
3) You detect a peak on a mass spectrum of a pure monatomic element near m/z: 28. Which isotope would you expect that this peak represents?
- Silicon-28 (A: 28 Z: 14)
- Nickel-58 (A: 58 Z: 28)
4) You insert a sample consisting of aluminum-27 atoms into a mass spectrometer. These atoms lose one electron each to become cations. At what mass/charge ratio do you expect to see a peak in the mass spectrum?
- m/z: 26
- m/z: 27
- m/z: 28
- m/z: 13
5) Which of the following isotopes is consistent with the knowledge that a particular atom has 7 protons and 8 neutrons? Consult the IUPAC Periodic Table of the Elements and Isotopes Learning Tool if needed.
6) Sulfur-36 and argon-36:
- Have the same mass number and have the same number of neutrons
- Have the same mass number and do not have the same number of neutrons
- Have the same atomic number and have the same number of neutrons
- Have the same atomic number and do not have the same number of neutrons