Chemistry 2e

# Key Terms

Chemistry 2eKey Terms
actinide
inner transition metal in the bottom of the bottom two rows of the periodic table
alkali metal
element in group 1
alkaline earth metal
element in group 2
alpha particle (α particle)
positively charged particle consisting of two protons and two neutrons
anion
negatively charged atom or molecule (contains more electrons than protons)
atomic mass
average mass of atoms of an element, expressed in amu
atomic mass unit (amu)
(also, unified atomic mass unit, u, or Dalton, Da) unit of mass equal to $112112$ of the mass of a 12C atom
atomic number (Z)
number of protons in the nucleus of an atom
binary acid
compound that contains hydrogen and one other element, bonded in a way that imparts acidic properties to the compound (ability to release H+ ions when dissolved in water)
binary compound
compound containing two different elements.
cation
positively charged atom or molecule (contains fewer electrons than protons)
chalcogen
element in group 16
chemical symbol
one-, two-, or three-letter abbreviation used to represent an element or its atoms
covalent bond
attractive force between the nuclei of a molecule’s atoms and pairs of electrons between the atoms
covalent compound
(also, molecular compound) composed of molecules formed by atoms of two or more different elements
Dalton (Da)
alternative unit equivalent to the atomic mass unit
Dalton’s atomic theory
set of postulates that established the fundamental properties of atoms
electron
negatively charged, subatomic particle of relatively low mass located outside the nucleus
empirical formula
formula showing the composition of a compound given as the simplest whole-number ratio of atoms
fundamental unit of charge
(also called the elementary charge) equals the magnitude of the charge of an electron (e) with e = 1.602 $××$ 10−19 C
group
vertical column of the periodic table
halogen
element in group 17
hydrate
compound containing one or more water molecules bound within its crystals
inert gas
(also, noble gas) element in group 18
inner transition metal
(also, lanthanide or actinide) element in the bottom two rows; if in the first row, also called lanthanide, or if in the second row, also called actinide
ion
electrically charged atom or molecule (contains unequal numbers of protons and electrons)
ionic bond
electrostatic forces of attraction between the oppositely charged ions of an ionic compound
ionic compound
compound composed of cations and anions combined in ratios, yielding an electrically neutral substance
isomers
compounds with the same chemical formula but different structures
isotopes
atoms that contain the same number of protons but different numbers of neutrons
lanthanide
inner transition metal in the top of the bottom two rows of the periodic table
law of constant composition
(also, law of definite proportions) all samples of a pure compound contain the same elements in the same proportions by mass
law of definite proportions
(also, law of constant composition) all samples of a pure compound contain the same elements in the same proportions by mass
law of multiple proportions
when two elements react to form more than one compound, a fixed mass of one element will react with masses of the other element in a ratio of small whole numbers
main-group element
(also, representative element) element in groups 1, 2, and 13–18
mass number (A)
sum of the numbers of neutrons and protons in the nucleus of an atom
metal
element that is shiny, malleable, good conductor of heat and electricity
metalloid
element that conducts heat and electricity moderately well, and possesses some properties of metals and some properties of nonmetals
molecular compound
(also, covalent compound) composed of molecules formed by atoms of two or more different elements
molecular formula
formula indicating the composition of a molecule of a compound and giving the actual number of atoms of each element in a molecule of the compound.
monatomic ion
ion composed of a single atom
neutron
uncharged, subatomic particle located in the nucleus
noble gas
(also, inert gas) element in group 18
nomenclature
system of rules for naming objects of interest
nonmetal
element that appears dull, poor conductor of heat and electricity
nucleus
massive, positively charged center of an atom made up of protons and neutrons
oxyacid
compound that contains hydrogen, oxygen, and one other element, bonded in a way that imparts acidic properties to the compound (ability to release H+ ions when dissolved in water)
oxyanion
polyatomic anion composed of a central atom bonded to oxygen atoms
period
(also, series) horizontal row of the periodic table
periodic law
properties of the elements are periodic function of their atomic numbers.
periodic table
table of the elements that places elements with similar chemical properties close together
pnictogen
element in group 15
polyatomic ion
ion composed of more than one atom
proton
positively charged, subatomic particle located in the nucleus
representative element
(also, main-group element) element in columns 1, 2, and 12–18
series
(also, period) horizontal row of the period table
spatial isomers
compounds in which the relative orientations of the atoms in space differ
structural formula
shows the atoms in a molecule and how they are connected
structural isomer
one of two substances that have the same molecular formula but different physical and chemical properties because their atoms are bonded differently
transition metal
element in groups 3–12 (more strictly defined, 3–11; see chapter on transition metals and coordination chemistry)
unified atomic mass unit (u)
alternative unit equivalent to the atomic mass unit