General chemistryLesson 3 of 7 in the course Atoms, Molecules, and Ions

Atomic Structure, Isotopes, and Mass Spectrometry

5 flashcards · 5 quiz questions · 5 match pairs · 5 fill-in sentences · English

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Summary

An atom has a small nucleus containing positively charged protons and uncharged neutrons. Negatively charged electrons occupy the space outside the nucleus. The nucleus contains almost all of an atom’s mass because protons and neutrons are much heavier than electrons. Electrons, however, occupy almost all of the atom’s volume.

An atom’s diameter is approximately 10−1010^{-10} m, while a nucleus is roughly 10−1510^{-15} m in diameter—about 100,000 times smaller. Imagine a blueberry-sized nucleus inside an atom the size of a football stadium. This analogy illustrates how much empty space exists within an atom.

All flashcards

What is the relationship between the u, dalton, and amu?
They are equivalent names for an atomic-scale mass unit; one u is exactly one-twelfth the mass of a carbon-12 atom.
What is the elementary charge?
The magnitude of the charge of a proton or electron, approximately 1.602×10−191.602 \times 10^{-19} C.
Why is periodic-table atomic mass usually not a whole number?
It is a weighted average of the masses of naturally occurring isotopes and their abundances.
What does mass defect mean?
The mass of a nucleus is slightly less than the combined masses of its separate protons and neutrons.
How can isotopes function as tracers?
Researchers follow an isotope through a process to investigate where atoms go or how reactions occur.

Quiz questions

  1. What does the atomic number of an element specify?Answer: The number of protons in its nucleus.
  2. An atom has mass number 37 and atomic number 17. How many neutrons does its nucleus contain?Answer: 20
  3. An oxygen ion has atomic number 8 and charge 2−2-. How many electrons does it have?Answer: 10
  4. How is an element’s average atomic mass calculated from isotope data?Answer: Multiply each isotope mass by its fractional abundance, then add the products.
  5. What property does a mass spectrometer use to distinguish ions?Answer: Their mass-to-charge ratios.

Based on Chemistry 2e by Paul Flowers, Klaus Theopold, Richard Langley, William R. Robinson, PhD (OpenStax), licensed CC BY 4.0. Adapted into a summary, flashcards and quizzes.

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