Template:HideTOC 4.1: Cutting Alumimun until you get Atoms Take some aluminum foil. Cut it in half. Now you have two smaller pieces of aluminum foil. Cut one of the pieces in half again. Cut one of those smaller pieces in half again. Continue cutting, making smaller and smaller pieces of aluminum foil. 4.1.1: Indivisible - The Atomic Theory 4.2: The Nuclear Atom While Dalton's Atomic Theory held up well, J. J. Thomson demonstrate that his theory was not the entire story. He suggested that the small, negatively charged particles making up the cathode ray were actually pieces of atoms. He called these pieces "corpuscles," although today we know them as electrons. Thanks to his clever experiments and careful reasoning, J. J. Thomson is credited with the discovery of the electron. 4.2.1: The Properties of Protons, Neutrons, and Electrons 4.2.2: Isotopes - When the Number of Neutrons Varies 4.2.3: Elements- Defined by Their Number of Protons 4.2.4: Practice Isotopes 4.3: 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). 4.4: Ions - Losing and Gaining Electrons Atom may lose valence electrons quite to obtain a lower shell that contains an octet. Atoms that lose electrons acquire a positive charge as a result because they are left with fewer negatively charged electrons to balance the positive charges of the protons in the nucleus. Positively charged ions are called cations. Most metals become cations when they make ionic compounds. 4.4.1: Practice Ions 4.5: Electronic Structure and the Periodic Table The arrangement of electrons in atoms is responsible for the shape of the periodic table. Electron configurations can be predicted by the position of an atom on the periodic table. 4.5.1: Practice Electronic Structure 4.6: Periodic Trends- Atomic Radius 4.6.1: Periodic Trends- Ionization Energy 4.6.2: Metallic and Nonmetallic Character 4.6.3: Practice Trends 4.7: Calculating Atomic Mass 4.7.1: Practice Atomic Mass Template:HideTOC