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82 terms

Chemistry 521A - Midterm Review (Version II)

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Chemical formula
shows the kinds and numbers of atoms in the smallest representative unit of a substance
Valence electrons
electrons in the highest occupied energy level of an element's atoms
Electron Dot Structure
A diagram tha tshows valence electrons as dots
Octet Rule
In forming compounds, atoms tend to react so as to acquire the stable electron configuration of a noble gas
Halide ion
a negative ion formed when a halogen atom gains an electron
Formula Unit
the lowest whole-number ratio of ions in an ionic compound
Ionic bonds
the electrostatic attraction that binds oppositely charged ions together
Coordination Number
the number of ions of opposite charge that surround the ion in a crystal
metallic bonds
the attraction of free-floating valence electrosn for positively charged metal ions
Ionic compounds
compounds composed of cations and anions
Alloy
a mixture of two or more elements, at least one of which is a metal
Anions
negatively charged ions
Cations
positively charged ions
Molecule
an electrically neutral group of atoms joined together by covalent bonds
Molecular Compound
compound composed of molecules
Covalent Bond
joins atoms held together by sharing electrons
Diatomic molecule
a molecule composed of two atoms
Molecular formula
shows the kinds and numbers present in a molecule of a compound
Single Covalent Bond
a chemical bond in which only one pair of electrons is shared by two bonded atoms
Structural formula
a chemical formula that shows the arrangement of atoms in a molecule or polyatomic ion
bond dissociation energy
the amount of energy required to break a covalent bond between atoms
Polyatomic ion
a tightly bound group of atoms taht has a positive or negative charge and behaves as a unit
Coordinate covalent bond
a covalent bond in which one atom contributes both bonding electrons
VESPR Theory
states that because electron pairs repel, molecules adjust their shapes so that valence-electron pairs are as far apart as possible
linear molecule
a term used to describe the shape of certain molecules such as CO2
sigma bond
a bond formed when two atomic orbitals combine to form a molecular orbital that is symmetrical along the axis connecting the two atomic nuclei
pi bond
a bond in which the bonding electrons are most likely to be found in the sausage-shaped regions above and below the nuclei of the bonded atoms
hybridization
a process in which several atomic orbitals overlap to form the same number of equivalent hybrid orbitals
nonpolar covalent bond
a bond formed when the atoms in a molecule are alike and the bonding electrons are shared equally
polar covalent bond
a bond formed when two different atoms are joined by covalent bond and the bonding electrons are shared unequally
polar molecule
a molecule in which one end is slightly positive and the other is slightly negative
van der Waals forces
a term used to describe the weakest intermolecular attractions; these include dispersion forces and dipole interactions
network solid
a substance in which all of the atoms are covalently bonded to each other
double covalent bond
a bond in which two atoms share two pairs of electrons
dispersion force
attractions between molecules caused by the electron motion on one molecule affecting the electron motion on the other through electrical forces; they are the weakest interactions between molecules
triple covalent bond
a bond in which three pairs of electrons are shared by two atoms
hydrogen bond
attractive forces in which a hydrogen covalently bonded to a very electron negative atom is also weakly bonded to an unshared electron pair of another electronegative atom
resonance structure
one of the two or more equally valid electron dot structures of a molecule or a polyatomic ion
dipole
a molecule that has two poles or regions with opposite charges
unshared pairs
a pair of valence electrons that is not shared between atoms
electronegativity
a relative measure of an atom's ability to attract the shared electrons in a chemical bond
bond energy
the amount of energy required to break a specific bond in one mole of molecule, given in kJ/mole
valence electrons
an electron that occupies the outermost energy level or shell of an atom
Lewis Structures
a symbolic representation of the arrangement of the valence electrons of an element or compound
octet rule
states that when bonds form, atoms gain, lose or share electrons in such as way as to achieve an octet or filled energy level
Periodic Law
when the elements are arranged in order of increasing atomic number, there is a periodic repetition of their physical and chemical properties
Metals
good conductors of heat and electric current; metals tend to be shiny, ductile, and malleable
Non-metals
poor conductors of heat and electric current
Metalloids
have properties that are similar to those of metals and nonmetals
alkali metals
any metal in group 1A of the periodic table
alkaline earth metals
any metal in group 2A of the periodic table
noble gases
an element in group 8A of the periodic table; the s and p sublevels of the highest occupied energy level are filled
representative elements
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 an p sublevels in the highest occupied energy level are partially filled
transition metals
one of the group B elements in which the highest occupied s sublevel and a nearby d sublevel generally contain electrons
inner transition metals
an element in the lanthanide or actinide series; the highest occupied s subevel and a nearby f sublevel of its atoms generally contain electrons; also called inner transition element
period
a horizontal row of elements in the periodic table
group
a vertical column of elements in the periodic table
Periodic table
an arrangement of elements in which the elements are separated into groups based on a set of repeating properties
halogens
non-metals of group 7A
ion
an atom of group of atoms that has a positive or negative charge
anion
any atom of group of atoms with a negative charge
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
cation
any atom or group of atoms with a positive charge
ionization energy
the energy required to remove an electron from an atom in its gaseous state
ionic radius
decreases for cations and anions from left to right across a period
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; described the structure and chemical reactivity of matter in terms of atoms
Democritus
Greek philosopher who was among the first to suggest the existence of atoms
Scanning Tunneling microscope
an instrument used to generate images of individual atoms
electrons
negatively charged subatomic particles
cathode ray
stream of electrons produced at the negative electrode of a tube containing a gas at low pressure
protons
positively charged subatomic particles
neutrons
subatomic particles with no charge
nucleus
the central core of the atom which is made up of protons and neutrons
atomic number
the number of protons in the nucleus of an atom of an element
mass number
the total number of protons and neutrons in the nucleus of an atom
isotopes
atoms of the same element have the same atomic number of different atomic masses due to a different number of neutrons
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
Atomic number
a number equal to the number of protons as well as the number of electrons in an atom
Number of neutrons
Equal to the mass number minus the atomic number