Chapter 6 Flashcards
chemical bond
attraction between nuclei and valence electrons of different atoms
how do atoms form compounds?
by gaining, losing, or sharing electrons
ionic bond
attraction between cations and anions
cation
metal
anion
nonmetal
covalent bond
sharing electrons between two nonmetals
non-polar covalent
bonding electrons are shared equally between bonding atoms
polar covalent
bonded atoms have an unequal attraction for shared electrons
list the bonds in order from least to greatest electronegative difference
non-polar covalent, polar covalent, ionic
molecule
neutral group of atoms held together by covalent bonds
molecular compound
chemical compound whose simplest units are molecules
chemical formula
indicates relative number of atoms of each kind in a chemical compound
molecular formula
shows types and numbers of atoms combined in a single molecule of a molecular compound
when do atoms have lower potential energy?
when bonded to other atoms
bond length
average distance between two bonded atoms at minimum potential energy
when do atoms release energy?
they release energy when forming covalent bonds
energy must be ______ to separate bonded atoms
added
when forming a covalent bond…
atoms’ shared electrons form overlapping orbitals
why do overlapping orbitals form?
achieves noble gas configuration/ stability
why are noble gases unreactive?
electron configurations are stable
how do atoms fill outermost p and s orbitals?
by sharing electrons through covalent bonding
exceptions to the octet rule?
some atoms can’t fit 8 valence electrons; others can fit more
how many electrons does Hydrogen need to form a bond and be stable?
only two
expanded valence
main group elements in periods three and up can form bonds involving more than 8 electrons
list the number of bonds in order of least to greatest energies
single < double < triple
resonance
other ways to write a Lewis form
ionic compound
cations and ions combined so the number of positive and negative charges are equal
what form do most ionic compounds exist as?
crystaline solids
can ionic compounds be separated into independent neutral units?
no
empirieal formula
simplest ratio of compound’s ions
mula unit
simplest collection of atoms from which ionic compound’s formula can be established
Avagadro’s number
6.022 x 10^23
how do ions minimize their potential energy?
by forming a crystal lattice
crystal lattice
attractive forces exist between oppositely charged ions within a lattice; repulsive forces exist between like-charged ions
what does combined repulsive forces within crystal lattices determine?
distance between ions and pattern of ions’ arrangement in crystal lattice
differences between ionic and molecular compounds?
- force that holds ions together in ionic compound is stronger than the one that holds together molecular compounds
- molecular compounds melt at lower temps
ionic compound properties
- solids at room temp
- very high melting point
- hard but brittle
- not electrical conductors in solid state because ions can’t move
polyatomic ions
charged group of covalently bonded atoms
metallic bonding properties
- conductors of electricity
- conductors of heat
- malleability
- ductility
- shiny appearance
metallic properties
- electricity conductors
- thermal conductors
- malleable
= ductile - shiny appearance
delocalized electrons
electrons don’t belong to any one atom but are free to move freely about the metals’ network of empty atomic orbitals; forms a “sea of electrons” which then forms a crystal lattice
metallic bonding
chemical bodning resulting from attraction between metal atoms and surrounding sea of electrons
molecular geometry
3 d arrangement of molecules’ atoms with regular patterns and equal distances separating atoms not bonded to each other
what two factors determine an electron’s polarity?
molecular shape and difference in electronegativity of the atoms
VSPER theory
in a small molecule, pairs of valence electrons are arranged as far apart from each other as possible
what does VSPER stand for?
Valence Shell Electron Pair Repulsion
bond angle
geometric angle between 2 adjacent bonds
linear
form a straight line; central atom bonded to two atoms with NO unshared pairs
o-o
trigonal planar
flat triangle; atom has no unshared pairs of electrons o
|
o
/ \
o o
bond angle of linear
180
bond angle of trigonal planar
120
tetrahedral
four surfaces; central angle bonded to four atoms, and central atom has no unshared pairs of electrons o
|
o
/ | \
o o o
trigonal-pyramidal
central atom bonded to three other atoms and HAS an unshared pair of electrons
at is true of trigonal-pyramidal models?
unshared pairs of electrons exert greater repulsion force because they’re held by only one atom
bond angle of tetrahedral
109.5
bond angle of trigonal-pyramidal
107
bent
central atom bonded to two other atoms and has TWO unshared pairs of valence electronsq
bond angle of bent
105
atomic orbital
region around nucleus where electrons with a given energy are most likely to be found
hybrid orbital
mixture of atomic orbitals formed when atoms approach each other to form a bond
sp orbital
formed in linear molecules from mixing s and p orbitals
sp^2
formed in trigonal planar molecules from mixing s and 2p orbitals
sp^3
formed in tetrahedral, pyramidal, and bent molecules by mixing s and 3p orbitals
intermolecular forces
force of attraction between molecules
strength of intermolecular forces?
generally weaker than ionic, covalent, and metallic
what is one measure of intermolecular forces?
boiling point; a higher boiling point shows higher attractive forces
dipole
separation of two opposite charges by some distance
induced dipole
created by presence of neighboring dipole
dispersion force
force of attraction between neighboring dipoles
do larger or smaller atoms have greater dispersion forces?
larger
dipole-dipole force
attraction between opposite charges of neighboring permanent dipoles
polar molecule has _________ dipoles
permanent
what increases dipole moment?
greater difference in electronegativity
Hydrogen bonding
force of attraction between Hydrogen and either Fluorine, Oxygen, or Nitrogen
Hydrogen
one of the least electronegative elements
Fluorine, Oxygen, NItrogen
the most electronegative elements
strength of Hydrogen bonds
very strong
