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

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