Section 1 review
All matter is made up of fundamental building blocks called atoms. The properties of matter are determined by the structure of the atoms within it. Within each atom are elementary particles: protons, neutrons, and electrons. Scattering experiments show that the nucleus is small, massive, and positively charged. The orbit of the electron around the nucleus is maintained by the electric force between the negatively charged electrons and the positively charged protons in the nucleus. All atoms of a particular element have the same atomic number (and hence have the same number of protons and electrons), but they may be different isotopes depending on the number of neutrons in the nucleus. The atomic mass number of an isotope is the sum of the number of protons and neutrons. Read the text aloud
atom, electron, proton, neutron, atomic number, elementary charge, nucleus, isotopes, mass number

A=Z+N

Review problems and questions

  1. Describe the evidence that demonstrates why we know the nucleus of an atom is small, is massive, and contains positive charge. Read the text aloud Show
  1. Describe the history of at least three changes in our understanding of the properties of the atom since 1850. Read the text aloud Show
  1. What property of atoms determines the overall organization of the periodic table of the elements? Read the text aloud Show
  1. Compare the three primary elementary particles (protons, neutrons, and electrons) on the basis of their location within an atom, relative mass, and charge. Read the text aloud Show
  1. An element has a mass number A = 84 and a neutron number N = 48. Which element is this? Read the text aloud Show
  1. An atom is made up of 19 protons and 20 neutrons. What is the total mass of this atom?
    1. 6.528×10−29 kg
    2. 6.528×10−26 kg
    3. 6.528×10−27 kg
    4. 3.350×10−26 kg Read the text aloud Show
  1. The proton is approximately 1,836 times more massive than the electron. If we calculate the mass of an atom by considering only the mass of the protons and the neutrons, what is the percent error introduced in the calculation? Read the text aloud Show

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