Term | Definition |
Periodic Table of Elements | a table showing the chemical elements arranged in order of increasing atomic number |
element | a pure substance that cannot be separated into simpler substances by physical or chemical means |
chemical symbol | a one- or two-letter notation used to represent an atom of a particular element |
atomic number | the number of protons in the nucleus of one atom of an element; identifies the atom |
atomic mass | the average mass of protons and neutrons in an element; always round this number |
groups | The vertical columns on a Periodic Table -- They arrange the elements by the number of electrons in the outermost shell. |
periods | The horizontal rows in a Periodic Table -- They classify the elements by the number of electron shells. |
metals | elements that are typically solid, lustrous, malleable, and good conductors |
nonmetals | elements that are typically not lustrous, usually a gas or brittle solid, not malleable, and poor conductors |
metalloids | elements that have properties of both metals and non-metals and are found on the "steps" of the PTE |
noble gases | unreactive nonmetals in Group 18 of the Period Table; they won't even burn |
electron shell | a specific area where electrons of the same energy level are found |
valence electrons | the electrons in the outermost energy level -- They influence how an atom will react with other atoms |
protons and neutrons | the two subatomic particles that contribute to the mass of an atom |
reactivity | rate at which a chemical substance tends to react |
net charge | the sum of the positive and negative charges in an atom |
ion | an atom that has gained or lost an electron and now has a net charge, either positive or negative |
vertical | standing upright |
horizontal | parallel to the horizon (line between sky and sea); flat |
highly reactive | describes an element that reacts quickly and/or easily with other atoms |
less reactive/more stable | describes an element that reacts slowly with other atoms |
stable | describes an element that does not react with other elements |
outermost energy level | determines the chemical properties of the atom because of the "rule of 8"; also called the valence shell |