CHAPTERS 18 & 20 ATOMS AND THE PERIODIC TABLE

MODELS OF THE ATOM 1. Dalton’s Model: proposed the first model of atoms in the early 1800’s; thought atoms were a solid sphere 2. Thompson’s Model: in 1904, he discovered the electron, he imagined electrons stuck in the atom’s surface like chocolate chips in a ball of cookie dough 3. Rutherford’s Model: in 1911, he showed that an atom’s mass is concentrated in the nucleus made of protons surrounded by electrons.

4. Bohr’s Model: in 1913, he hypothesized that electrons traveled in fixed orbits around the atom’s nucleus, he concluded the nucleus contained protons and neutrons 5. Electron Cloud Model: current theory; the rapid and random motion of electrons creates an electron cloud around the nucleus

ATOMS 1. The smallest piece of matter that still has the properties of the element a. Proton: positively charged particle located in the nucleus b. Neutron: neutral particle located in the nucleus c. Electron: negatively charged particle that surrounds the nucleus in the electron cloud d. Quarks: the smaller particles that make up the protons and neutrons

STRUCTURE OF THE ATOM I. Nucleus A. positively charged, tightly packed cluster of protons and neutrons held together by the strong force 2. Atomic Mass A. nucleus contains most of the mass B. atomic mass unit 1. Unit used to measure the mass of an atom

3. Atomic Number A. number of protons in an atom B. tells you what element you have 4. Mass Number A. total number of protons and neutrons B. number of neutrons equals the mass number minus the atomic number

5. Electrons A. number of electrons in an atom is the same as the atomic number 6. Chemical Symbol A. abbreviation of an element

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THE PERIODIC TABLE I. Organizing The Periodic Table A. Dmitri Mendeleev, in the late 1800s, organized the elements by increasing atomic mass B. In 1913, Henry Mosely arranged the elements based on atomic number

C. Groups/Families vertical columns 2. Elements in each group have similar properties 3. All atoms in a group have the same number of electrons in the outer energy level, they are called valence electrons; this determines the properties of the atom

D. Periods 1. 7 horizontal rows 2. The number of energy levels in an atom is the same as the row number 3. Each of the seven energy levels can have a maximum number of electrons a. Energy level one can have no more than 2 electrons b. Energy level two can have no more than 8 electrons

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REGIONS OF THE PERIODIC TABLE A. METALS 1. Located to the left of the zig-zag or stair step line 2. Most are solids at room temperature, the exception is Mercury (Hg); it is a liquid at room temperature

B. NONMETALS 1. Located to the right of the zig-zag or stair step line 2. Most are gases C. METALLOIDS 1. Located on either side of the zig-zag or stair step line

METALS A. Properties 1. Have luster, conduct heat and electricity, malleable, ductile 2. Tend to lose electrons in reactions to form positive ions B. Groups of Metals 1. Alkali Metals a. Group 1 b. Very reactive c. Combine easily with group 17 (halogens) to form salts 2. Alkaline Earth Metals a. Group 2 3. Transition Metals a. Groups Rare Earth Metals a. Two separate rows at the bottom

NONMETALS A. Properties 1. Dull, brittle, poor conductors of heat & electricity 2. Tend to gain electrons in reactions to form negative ions B. Hydrogen 1. The most common element in the universe

C. Groups of Nonmetals 1. Boron Group--group Carbon Group--group Nitrogen Group--group Oxygen Group--group Halogens--group Noble Gases--group Exist as gases in the atmosphere 2. Do not form compounds with other elements

METALLOIDS A. Properties 1. Have properties of both metals and nonmetals

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