Download Glossary of Key Terms in Chapter Two

Glossary of Key Terms in Chapter Two
alkali metal (2.4) occupy group IA (1) of the periodic table.
alkaline earth metal (2.4) occupy group IIA (2) of the periodic table.
anion (2.1 ) a negatively charged atom or group of atoms.
atom (2.1) the smallest unit of an element that retains properties of that element.
atomic mass (2.1) the mass of the atom expressed in atomic mass units.
atomic number (2.1) the number of protons in the nucleus of an atom. It is a characteristic identifier of an
element.
atomic orbital (2.4) a specific region of space where an electron may be found.
cathode rays (2.1) a stream of electrons that are given off by the cathode (negative electrode) in a cathode
ray tube.
cation (2.1) a positively charged atom or group of atoms.
electron (2.1 ) a negatively charged particle outside of the nucleus of an atom.
electron affinity (2.6) the energy released when an electron is added to an isolated atom.
electron configuration (2.4) the arrangement of electrons in atomic orbitals.
energy levels (2.3) one of the numerous atomic regions where electrons may be found.
group (2.4) any one of 18 vertical columns of elements. (Note that a group is often referred to as a family.)
halogen (2.4) occupy group VIIA (17) of the periodic table.
ion (2.1) an electrically charged particle that is formed by the gain or loss of an electron.
ionization energy (2.6) the energy needed to remove an electron from an atom in the gas phase.
isoelectronic (2.6) atoms, ions, and molecules containing the same number of electrons.
isotope (2.1 ) atom of the same element that differs in mass because it contains different numbers of
neutrons.
mass number (2.1 ) the sum of the number of protons and neutrons in an atom.
metal (2.4) element located on the left side of the periodic table (left of the “staircase” boundary).
metalloid (2.4) an element along the “staircase” boundary between metals and nonmetals; they exhibit both
metallic and nonmetallic properties.
neutron (2.1 ) an uncharged particle, with the same mass as the proton, found in the nucleus of an atom.
noble gas (2.4) elements in group VIIIA (18) of the periodic table.
nonmetal (2.4) element located on the right side of the periodic table (right of the “staircase” boundary).
nucleus (2.1 ) the small, dense center of positive charge in the atom.
octet rule (2.6) a rule predicting that atoms form the most stable molecules or ions when they are
surrounded by eight electrons in their highest occupied energy level.
period (2.4) any one of seven horizontal rows of elements in the periodic table.
periodic law (2.4) a law stating that properties of elements are periodic functions of their atomic numbers.
(Note that Mendeleev’s original statement was based on atomic masses.)
proton (2.1) a positively charged particle in the nucleus of an atom.
quantization (2.3) a characteristic that energy can occur only in discrete units called quanta.
representative element (2.4) member of the group of the periodic table designated as “A”.
sublevel (2.4) set of equal-energy orbitals within a principal energy level.
transition element (2.4) occurs between groups IIIB (3) and IIB (12) in the long period of the periodic
table.
valence electron (2.4) electron in the outermost shell (principal quantum level) of an atom.