the chart scientists use to organize and classify all the known elements
Periodic Table
a pure substance that cannot be broken down into simpler substances by chemical reactions
Element
the one- or two-letter representation of an element
Element Symbol
the number of protons in the nucleus of an atom
Atomic Number
approximately equal to the number of protons and neutrons
Atomic Mass
one of the horizontal rows in the periodic table
Period
vertical columns of elements (families) on the periodic table with similar valence electron configurations and similar properties
Groups
vertical columns of elements (groups) on the periodic table with similar valence electron configurations and similar properties
Family
a set of symbols used to describe the elements within a substance
Chemical Formula
a shiny, dense substance that easily conducts heat and electricity
Metals
elements that are poor electrical conductors and tend to accept electrons easily
Nonmetals
elements that lie between the metals and the nonmetals on the periodic table; these element exhibit both metallic and nonmetallic properties
Metalloids
six elemental gasses that do not naturally react with other elements
Noble Gases
the tendency of two or more chemicals to react
Reactivity
a characteristic of a substance that is measurable or observable during a chemical reaction
Chemical Property
a characteristic used to describe matter that can be observed (such as texture, color, and odor) or measured (such as mass, length, and volume) without changing its composition
Physical Property
a Russian scientist who organized and classified the elements based on similar physical and chemical properties; his work was the basis for the modern periodic table of the elements
Dmitri Mendeleev
a subatomic particle with a positive charge that is located in the nucleus of an atom
Proton
the smallest unit of an element that has the properties of that element
Atom
the path or orbit electrons follow around the nucleus of an atom
Electron Shell