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General Chemistry Ch. 3 - Bonding and Chemical Interactions
MCAT
28
Chemistry
Undergraduate 1
03/21/2016

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Term
What is the octet rule?
What are the exceptions?
Definition
The octet rule states than an atom tends to bond with others atoms so that it has 8 electrons in its outermost shell.

Incomplete octet-elements stable with fewer than 8 electrons: Hydrogen (2), Helium (2), lithium (2), beryllium (4), boron (6)

expanded octet-an element in period 3 and great can hold more than 8 electrons

odd numbers of electrons-any molecule with an odd number of valence electrons can't distribute them evenly to give 8 to each element
Term
ionic bonding
Definition
electrons are transferred from one element, typically a metal (low ionization energy), to another element, typically nonmetal (high electron affinity). The resulting force holding them together is between the opposite charges. This bonding creates lattice structures.
Term
covalent bonding
Definition
an electron pair is shared between two atoms. Nonpolar is equal sharing. Polar is unequal sharing.
Term
coordinate covalent bond
Definition
a covalent bond in which both electrons come from the same atom.
Term
cation
Definition
atom that loses an electron and is positive
Term
anion
Definition
atom that gains electrons and is negative
Term
characteristic physical properties of ionic compounds
Definition
-high melting point
-high BP
-aqueous state are good conductors
-ready dissolve in aqueous solvent
-form crystalline lattice
Term
covalent bond length
Definition
distance between two nuclei; single bond is the longest/weakest and triple bond is the shortest/strongest
Term
covalent bond energy
Definition
energy needed to break bonds between components; the higher the energy the stronger the bond
Term
bond polarity
Definition
due to differences in electronegativity; forms a dipole
Term
dipole moment
Definition
vector quantity of a polar bond or polar molecule that represents the polarity of a dipole
Term
Lewis structure
Definition
chemical symbol of an element surrounded by dots representing its s and p orbital electrons
Term
formal charge
Definition
normal number of electrons in the atom's valence shell minus the number of nonbonding electrons minus half the number of bonding electrons. Formal charge underestimates teh effect of electronegativity in assuming perfect electron sharing. Oxidation numbers overestimate electronegativity in assuming 100% share to one atom
Term
Rules for assessing stability of resonance structures
Definition
-a lewis structure with small or no formal charges is preferred over a structure with large formal charges

-less separation between opposite charges is preferred over a Lewis structure with a large separation of opposite charges

-a lewis structure in which negative formal charges are placed on more electronegative atoms is more stable than one in which the negative formal charges are placed on less electronegative atoms
Term
Valence shell electron pair repulsion (VSEPR) theory
Definition
theory that uses lewis dot structures to predict the molecular geometry of covalently bonded molecules
Term
electronic geometry
Definition
describes the spatial arrangement of all pairs of electrons around the central atom, bonded or not; lone electron pairs take up more space than bonding electrons thus decreasing bond angles
Term
molecular geometry
Definition
describes spatial arrangement of only the bonding pairs of electrons
Term
linear
Definition
two bonded or nonbonded pairs of electrons (electronic geometry); 180 degree bond angle
Term
trigonal planar
Definition
three bonded or nonbonded pairs of electrons (electronic geometry); 120 degree bond angle
Term
tetrahedral
Definition
four bonded or nonbonded pairs of electrons (electronic geometry); 109.5 degree bond angle
Term
trigonal bipyramidal
Definition
five bonded or nonbonded pairs of electrons (electronic geometry); 90, 120 and 180 degree bond angles
Term
octahedral
Definition
six bonded or nonbonded pairs of electrons (electronic geometry); 90 and 180 degree bond angles
Term
polarity of molecules
Definition
consider vector addition of bond dipole moments when figuring overall molecular polarity; if all dipole moments cancel out molecule is nonpolar; if they don't cancel out there will be a net dipole moment equal to the sum of the vectors
Term
What are the quantum numbers
Definition
principal quantum number (n) n = 1,2,3... - main energy level or shell

angular momentum quantum number (l) l = 0...n-1 - referred to as subshells; l=0 s-orbital, l=1 p-orbital

magnetic quantum number (m(sub)l) ml = -l to +l - the orientation of the electron

spin quantum number (m(sub)s) ms = +1/2 or -1/2, up or down spin respectively
Term
intermolecular forces
Definition
london dispersion forces, dipole-dipole interactions, hydrogen bonds
Term
london dispersion forces
Definition
results from electron density being unequally distributed between two atoms causing tiny rapid polarization and depolarization
Term
dipole-dipole interactions
Definition
interactions between polar and nonpolar parts of molecules
Term
hydrogen bonds
Definition
when H bonds to N, O or F due to huge differences in electronegativity
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