Chapter 2 Outline


This chapter serves as an introduction to atomic theory. The most important concept in this chapter is the idea that everything is composed of atoms. And that there are different types of atoms (elements). This concept is the one of the underlying theories that makes modern chemistry possible. It is the context that allows us to explain what happens.

  1. Imaging and Moving Individual Atoms
  2. Modern Atomic Theory and the Laws That Led to It
  3. The Discovery of the Electron. This section outlines the ground breaking experiments that lead to the discovery of the electron. You should be familiar with the experiments, how they work and what they explain. The names in this section are some of the greatest in science.

  4. The Structure of the Atom. This section describes the experiments that lead to understanding the structure of the atom. You should be familiar with the experiments, how they work and what they explain.
  5. Subatomic Particles: Protons, Neutrons and Electrons in Atoms. This section explains how subatomic particles are arranged to make atoms and elements. You should be able to identify the number of protons, neutrons, and electrons in an atom of a given element. The most important points are outlined in the table below.

    Subatomic Particles
    Particle Charge Mass Symbol Significance
    Proton +1 1 u  11p Atomic Number
    Neutron 0 1 u 10n # neutron + # proton = isotope mass
    Electron -1 0 u (0.0005485799 u) 0-1e charge of atom

  6. Finding Patterns: The Periodic Law and the Periodic Table. This section describes the arrangment of elements in the periodic table and the development of the periodic table. This section discusses the gerneral trends in the periodic table. You should be able to locate each of the groups discussed on a periodic table.

  7. Atomic Mass: The Average Mass of an Element's Atoms. The identity of an element is determined by the atomic number or the number of protons. However, the number of neutrons is not fixed. Atoms of a given element with different numbers of neutrons are called isotopes. They are chemically identical (almost), but they have slightly different masses. In this section you will need to do calculations with percent abundance.In this section you will calculate the atomic weight for an element. This is a weighted average of the mass for each isotope. Follow the exaples carefully and make certain you understand where the numbers are coming from.

  8. Molar Mass: Counting Atoms by Weighing THem. This section introduces the concept of the mole and of molar mass. This is a key concept in the course. You will use it throughout the year. Understanding what the mole is about is critical to solving modern chemistry problems. The key point is that the mole is a counting unit (like pair, dozen, score, gross). You need to be able to convert from moles to mass or from mass to moles. The section also discusses Avogadro's number. You will use this some, and you should realize how large it is. But it will not be used throught the semester.

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