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BJU Chemistry Ch 4
Bob Jones Chemistry - Chapter 4
Term | Definition |
---|---|
alpha particle | The nucleus of the helium atom (two protons, two neutrons) produced as the by-product of a nuclear decay process. |
anion | A negatively charged ion. |
atom | A neutral particle with a centrally located nucleus, consisting of protons and neutrons, with electrons around it; the smallest particle that makes up an element and that is capable of chemical interactions. |
atomic number (Z) | The number of protons in the nucleus of an atom. |
Aufbau principle | The principle that the electron configuration of an atom builds on those of lower atomic number. The electrons fill the sublevels in the order given by the diagonal rule. |
azimuthal quantum number (l) | The number that defines the symmetrical shapes that are arranged around the nucleus and that electrons may be found in; sometimes called the sublevel quantum number. |
cathode rays | The stream of electrons emitted from the cathode in a cathode-ray tube. |
cation | A positively charged ion. |
continuous spectrum | A complete visual spectrum with no frequency gaps emitted only by an ideal luminous object. |
de Broglie's hypothesis | The concept that if waves can behave like particles, then particles can also behave like waves. |
electron | A particle with a -1 charge and a mass of 9.11 x 10 -31 kg found orbiting the nucleus in an atom. |
electron configuration | The arrangement of electrons in an atom: a number indicates the principal energy level, a letter indicates the sublevel, and a superscript denotes the number of electrons contained within the sublevel. |
electron dot notation | A chemical symbol with surrounding dots representing the valence electrons of an atom. |
electron-spin quantum number | The number that describes the two possible "spin" states of a pair of electrons in an orbital. |
ground state | An atom's lowest energy state. |
Heisenberg uncertainty principle | The principal that it is impossible to know both the energy or momentum (velocity) and the exact position of an electron at the same time. |
Hund's rule | The rule stating that electrons fill a sublevel by placing a single electron in each orbital before adding a second electron to any orbital. |
isotope | One of two or more atoms of the same element with the same number of protons (atomic number) but with different numbers of neutrons. |
isotopic notation | A naming convention used to distinguish between different isotopes of elements. It includes the element's symbol, atomic number, and mass number and specifies the exact composition of an atom. |
law of definite composition | A law stating that every compound is formed of elements combined in mass ratios that are unique for that compound. |
line spectrum | A spectrum showing only certain colors or wavelengths of light. |
magnetic quantum number (m) | The number that defines the spatial orientation of the orbitals within a sublevel; sometimes called the orbital quantum number. |
mass number (A) | A whole number equal to the sum of the protons and neutrons in an atom. |
neutron (n) | A neutral particle in an atom's nucleus. It has a mass of 1.675 x 10 -27 kg, slightly greater than the mass of a proton. |
nucleus | The dense central part of an atom made up of protons and neutrons. It contains virtually all the atom's mass but only a small portion of its volume. |
orbital | A three-dimensional region of space around a nucleus in which as many as two electrons are likely to be found. Orbitals make up sublevels. |
orbital notation | An expression that represents the principal energy levels, sublevels, and orbitals for all the electrons in an atom using dashes and half arrows. |
Pauli exclusion principle | The rule that an orbital can hold only two electrons with opposite spin, resulting in a unique set of four quantum numbers for every electron in an atom. |
photon | A packet of electromagnetic energy modeled as a particle that transmits electromagnetic force in the standard model of matter. |
principal energy level | A region around the nucleus containing a specified group of electrons in sublevels and orbitals. |
principal quantum number (n) | The number indicating the main or principal energy level in which an electron is found. |
proton | A particle in an atom's nucleus with a +1 charge and mass of 1.673 x 10 -27 kg. |
quantized | Having to do with quantities in which there are only separate, discrete values allowed. |
quantum number | Four numbers that describe the location of an electron in an atom. |
sublevel | A portion of a principal energy level made up of one or more orbitals. |
unified atomic mass unit (u or amu) | A small unit of mass equal to one-twelfth the mass of the nucleus of a carbon-12 atom, or approximately the same size as a proton or a neutron. This unit is used to represent the mass of atoms and molecules. |
valence electron | One of the electrons usually found in the highest or outermost energy level of a neutral atom. They are loosely bound and are responsible for an atom's chemical behavior. |