2. I. Section 1
A. Atom: The smallest particle of an element.
B. Electron: The negatively charged
particles of an atom.
C. Nucleus: The center of the atom.
D. Protons: The positively charged
particles in the nucleus.
E. Neutrons: The neutrally charged particles in the nucleus that are the same size as the protons.

3. F. Energy Level: The specific amount of energy an electron has.
G. Atomic Number: The number of protons in an atom’s nucleus.
1. The number of protons equal
the number of electrons.
H. Mass Number: The
number of protons and neutrons in the nucleus of the atom.
I. Isotopes: Atoms of the same element with a different number of neutrons.

4. II. Section 2 A. Dmitri Mendeleev- Developed the
periodic table based on atomic masses.
B. Atomic Mass- the average mass of all
the isotopes of an element.
C. Periodic Table- an arrangement of elements showing the repeating pattern of their properties.
1. The modern periodic table is arranged by atomic number. Mosley developed this.

5. D. Period: A horizontal row of the periodic table.
Number of rings in the atom.
E. Group: A vertical column of the periodic table.
F. Chemical symbol: a representation of an element usually
Consisting of one
or two letters.

6. III. Section 3
A. Metal: Elements that are good conductors of electric current and heat, shiny and bendable.
B. Malleable: A material that can be
hammered or rolled into flat sheets
or other shapes.
C. Ductile: Material that can be
pulled out or drawn into a long wire.
D. Thermal conductivity: The ability of an object to transfer heat.
E. Electrical conductivity: The ability of an object to transfer electric current.

7. F. Reactivity: The ease and speed with which a substance reacts
F. Reactivity: The ease and speed with which a substance reacts with other substances.
G. Corrosion: The gradual wearing
away of a metal due to a chemical
reaction.
H. Alkali Metals: The metals in Group 1 not
including Hydrogen. They react by losing one
electron. Highly reactive.
I. Alkaline Earth Metals: Groups 2 elements of the periodic table. They react by losing two electrons.
J. Transition metals: Elements in Groups through 12.
K. Particle Accelerators: Powerful machines that move atomic nuclei faster and faster until they have reached very high speeds.

8. IV. Section 4
A. Nonmetals: Poor conductors of electric current and heat. Solid nonmetals are dull and brittle.
B. Diatomic Molecule: A molecule that consists of two atoms. NaCl, H2O
C. Halogens: Groups 17 elements that are
Called “salt-formers”.
D. Inert Gases: Groups 18 elements. Tend to
be un-reactive.
E. Semimetals: Have some properties of metals, but also have some properties of nonmetals Solids at room temp. brittle and hard.
F. Semiconductors: Substances that can conduct electric current under some conditions but not under others.

9. V. Section 5
A. Radioactive decay: A process in which the atomic nuclei of unstable isotopes release fast-moving particles and energy.
B. Radioactivity: The ability to spontaneously emit radiation.
C. Alpha particle: two protons and two neutrons with a positive charge.
D. Beta particle: a fast-moving electron given off by a nucleus during radioactive decay.
E. Gamma radiation: high-energy waves similar to X-rays.
F. Tracers: radioactive isotopes that can be followed through the steps of a chemical reaction or an industrial process.