| A | B |
|---|
| anion | any atom or group of atoms with a negative charge |
| atomic number | the number of protons in the nucleus of an atom of an element |
| cation | any atom or group of atoms with a positive charge |
| electron | a negatively charged subatomic particle |
| ion | an atom or gorup of atoms that has a positive or negative charge |
| isotope | atoms of the same element that have the same atomic number but different atomic masses due to a different number of neutrons |
| mass number | the total number of protons and neutrons in the nucelus of an atom |
| neutron | a subatomic particle with no charge and a mass of 1 amu; found in the nucleus of an atom |
| nucleus | the tiny, dense central portion of an atom, composed of protons and neutrons |
| proton | a positively charged subatomic particle found in the nucleus of an atom |
| atomic mass unit (amu) | a unit of mass equal to one-twelfth the mass of a carbon-12 atom |
| atomic mass | the weighted average of the masses of the isotopes of an element |
| photon | a quantum of light; a discrete bundle of electromagnetic energy that interacts with matter similarly to particles |
| ground state | the lowest possible energy of an atom described by quantum mechanics |
| atomic orbital | a mathematical expression describing the probability of finding an electron at various locations; usually represented by the region of space around the nucleus where there is a high probability of finding an electron |
| Pauli Exclusion Principle | an atomic orbital may describe at most two electrons, each with opposite spin direction |
| valence electrons | electrons in the highest occupied energy level of an atom |
| ionization energy | the energy required to remove an electron from an atom in its gaseous state |
| mole (mol) | the amount of a substance that contains 6.02 x 10^23 representative particles of that substance |
| molar mass | a term used to refer to the mass of a mole of any substance |
| atom | the smallest particle of an element that retains its identity in a chemical reaction |
| Dalton's atomic theory | the first theory to relate chemical changes to events at the atomic level |
| cathode ray | a stream of electrons produced at the negative electrode (cathode) of a tube containing a gas at low pressure |
| energy level | the specific energies an electron in an atom or other system can have |
| quantum | the amount of energy needed to move an electron from one energy level to another |
| quantum mechanical model | the modern description, primarily mathematical, of the behavior of electrons in atoms |
| electron configuration | the arrangement of electrons of an atom in its ground state into various orbitals around the nuclei of atoms |
| aufbau principle | the rule that electrons occupy the orbitals of lowest energy first |
| spin | a quantum mechanical property of electrons that may be thought of as clockwise or counterclockwise |
| Hund's rule | electrons occupy orbitals of the same energy in a way that makes the number or electrons with the same spin direction as large as possible |
| amplitude | the height of a wave’s crest |
| wavelength | the distance between adjacent crests of a wave |
| frequency | the number of wave cycles that pass a given point per unit of time; frequency and wavelength are inversely proportional to each other |
| hertz | the unit of frequency, equal to one cycle per second |
| electromagnetic radiation | energy waves that travel in a vacuum at a speed of 2.998 108 m/s; includes radio waves, microwaves, infrared waves, visible light, ultraviolet waves, X-rays, and gamma rays |
| spectrum | wavelengths of visible light that are separated when a beam of light passes through a prism; range of wavelengths of electromagnetic radiation |
| atomic emission spectrum | the pattern formed when light passes through a prism or diffraction grating to separate it into the different frequencies of light it contains |
| Planck's constant | a number used to calculate the radiant energy (E) absorbed or emitted by a body based on the frequency of radiation |
| photoelectric effect | the ejection of electrons by certain metals when they absorb light with a frequency above a threshold frequency |
| Heisenberg uncertainty principle | it is impossible to know exactly both the velocity and the position of a particle at the same time ( |
| periodic law | when the elements are arranged in order of increasing atomic number, there is a periodic repetition of their physical and chemical properties |
| metal | one of a class of elements that are good conductors of heat and electric current; metals tend to be ductile, malleable, and shiny |
| nonmetal | an element that tends to be a poor conductor of heat and electric current; nonmetals generally have properties opposite to those of metals |
| metalloid | an element that tends to have properties that are similar to those of metals and nonmetals |
| alkali metal | any metal in Group 1A of the periodic table |
| alkaline earth metal | any metal in Group 2A of the periodic table |
| halogen | a nonmetal in Group 7A of the periodic table |
| noble gas | an element in Group 8A of the periodic table; the s and p sublevels of the highest occupied energy level are filled |
| representative element | an element in an “A” group in the periodic table; as a group these elements display a wide range of physical and chemical properties. In their atoms, the s and p sublevels in the highest occupied energy level are partially filled |
| transition metal | one of the Group B elements in which the highest occupied s sublevel and a nearby d sublevel generally contain electrons |
| inner transition metal | an element in the lanthanide or actinide series; the highest occupied s sublevel and nearby f sublevel of its atoms generally contain electrons; also called inner transition element |
| atomic radius | one-half the distance between the nuclei of two atoms of the same element when the atoms are joined |
| electronegativity | the ability of an atom to attract electrons when the atom is in a compound |
| Avogadro's number | the number of representative particles contained in one mole of a substance; equal to 6.02 1023 particles |
| representative particle | the smallest unit into which a substance can be broken down without a change in composition, usually atoms, molecules, or ions |
| Avogadro's hypothesis | equal volumes of gases at the same temperature and pressure contain equal numbers of particles |
| percent composition | the percent by mass of each element in a compound |
