2: Atoms

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2.1: The Elements
All matter is composed of elements. Chemical elements are represented by a one- or two-letter symbol.
2.2: Looking for Patterns- The Periodic Table
Certain elemental properties become apparent in a survey of the periodic table as a whole. Every element can be classified as either a metal, a nonmetal, or a metalloid (or semi metal). A metal is a substance that is shiny, typically (but not always) silvery in color, and an excellent conductor of electricity and heat. Metals are also malleable (they can be beaten into thin sheets) and ductile (they can be drawn into thin wires).
2.3: The Structure of Atoms
Atoms are composed of three main subatomic particles: protons, neutrons, and electrons. Protons and neutrons are grouped together in the nucleus of an atom, while electrons orbit about the nucleus.
2.4: Nuclei of Atoms
Elements can be identified by their atomic number and mass number. Isotopes are atoms of the same element that have different masses.
2.5: Bohr Diagrams of Atoms and Ions
Bohr diagrams show electrons orbiting the nucleus of an atom somewhat like planets orbit around the sun. In the Bohr model, electrons are pictured as traveling in circles at different shells, depending on which element you have.
2.6: Atomic Masses
Atoms have a mass that is based largely on the number of protons and neutrons in their nucleus.
2.7: Periodic Trends- Atomic Radius
2.8: Periodic Trends- Ionization Energy
2.9: Radioactivity
Atoms are composed of subatomic particles—protons, neutrons, and electrons. Protons and neutrons are located in the nucleus and provide most of the mass of the atom, while electrons circle the nucleus in shells and subshells and account for an atom’s size. There are three main forms of radioactive emissions and are alpha particles, beta particles, and gamma rays.
2.E: Elements, Atoms, and the Periodic Table (Exercises)
These are homework exercises to accompany Chapter 2 of the Ball et al. "The Basics of GOB Chemistry" Textmap.
2.S: Elements, Atoms, and the Periodic Table (Summary)
To ensure that you understand the material in this chapter, you should review the meanings of the following bold terms and ask yourself how they relate to the topics in the chapter.