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