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Level 37

Chemical Bonding


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bond
a force that holds groups of 2 or more atoms together and allows them to function as a unit
covalent, ionic, metallic
3 types of bonds
electron configuration
Arrangement of electrons in an atom
octet rule
a concept of chemical bonding theory that is based on the assumption that atoms tend to have either empty valance shells or full valence shells of eight electrons
form ions and bond
the octet rule helps to explain why atoms
Covalent
Bonding Characteristic: Electrons are shared between 2 or 3 elements or compounds
molecular bonds
another name for covalent bonds
2 nuclei
sharing in covalent bonds occurs between
molecules
a group of atoms held together by covalent bonds
unshared pairs, bonding pairs
2 types of electron pairs that exist in covalent bonds
unshared pairs
pairs of electrons in covalent bonds that do not participate in bonding and belong to only 1 atom
lone pairs
another name for unshared pairs
bonding pairs
pairs of electrons that are shared between 2 atoms, thus creating a covalent bonds
Electronegativity
a measure of the ability of an atom in a chemical compound to attract electrons
having opposite ends
literal translation of polar
polar bonds
covalent bonds in which the bonding electrons are more strongly attracted by 1 of the bonding atoms
nonpolar bonds
covalent bonds in which the bonding electrons are shared equally between the 2 bonding atoms
not having opposite ends
literal translation of nonpolar
low
atoms that form metallic bonds have _______ ionization energies so that loosely held electrons are available for bonding
gases, liquids, or very soft solids
what are most covalent compounds at room temperature?
do not
covalent compounds _______ conduct electricity
brittle
covalent compounds are _______ when solid
nometals
covalent compounds typically form between
multiple
covalent compounds, unlike ionic bonds, can form _______ bonds
Single bond
1 pair of shared electrons
double bond
2 atoms share 4 electrons (2 pairs)
triple bond
2 atoms share 6 electrons (3 pair)
coordinate covalent bonds
a covalent bond in which a single atom contributes both of the electrons to a shared pair
sigma bonds, pi bonds
2 types of bonds covalent bonds are separated into
sigma
type of covalent bond that is formed along the horizontal axis between 2 atoms (primary bond)
pi
type of covalent bond that is formed above and below horizontal axis between 1 atoms (secondary bond)
1 sigma bond
single bonds consist of
double bonds consist of
1 sigma bond and 1 pi bond
triple bonds consist of
1 sigma bond and 2 pi bonds
positive and negative ions
when electrons are transferred, what is formed?
Cations
Ions with a positive charge.
anions
Elements which gain electrons become _______. (anions or cations)
electrostatic forces
cations and anions attract each other ->
ionic bonds
form from the attraction of oppositely charged ions.
formula unit
lowest whole number ratio of ion in an ionic compound
potential, balanced
ions in ionic compounds lower their _______ energy forming orderly, 3-D array in which the cations and anions are _______
repeating patterns
the formula units arrange themselves in _______ (crystal lattice or crystal lattice network)
Neutral
3rd degree substrate SN1 and E1
Solid
Fixed shape and size, atoms are close together, ordered structure, not compressible
High
E1 Temp
molten, solid
ionic compounds conduct electricity in the _______ state, but will not conduct electricity in the _______ state
Salts
Basic if there is a basic anion and a group 1 or 2 metal cation
electricity
The flow of electrons
soluble
A substance that can dissolve is said to be _______.
crystallize
breaking the solid into smaller pieces greatly increases its surface area
metals and nonmetals
ionic compounds typically form between
low, low
in ionic compounds, one atom has a _______ electronegativity and _______ electron affinity and the other is vice versa
monatomic ions
consists of a single ion
Polyatomic Ions
A group of atoms covalently bonded together which together have a charge that comes from either gained or lost electrons to gain an octet
0, 100, rarely
If the electronegativity difference is 0.00, the ratio is _______% Ionic and _______% covalent; this occurs _______
50, 50
If the electronegativity difference is < or equal to 1.7, the ratio is _______% Ionic and _______% covalent; this occurs _______
100, 0
If the electronegativity difference is >3.3, the ratio is _______% Ionic and _______% covalent; this occurs _______
0.4, 1.7
polar bonds: _______< or equal to x < _______
0.4
nonpolar bonds: <_______
vibrating
atoms are in continual _______ motion
bond length
the average distance between 2 bonded atoms
nucleus, nucleus
bond lengths are measured from the center of 1 _______ to the center of a neighboring _______
length
examples of scalars? (4)
atomic radius
A measure of the size of an element's atoms; usually the mean or typical distance from the nucleus to the boundary of the surrounding cloud of electrons.
fixed, vibrate
bond length and bond angle are not _______ because atoms _______ through bond in spring-like fashion
multiple bonds
what are shorter: multiple bonds or single bonds?
bond angle
angle between 2 bond axes
bond energy
energy required to break a bond
electrons
What is lost and gained in a redox reaction?
p orbitals
3 mutually perpendicular dumbbell shaped orbitals; second to fill from 2nd energy level on up; can hold max of 6 electrons
d orbitals
5 orbitals of cloverleaf shape; third to fill for any energy level; beginning in the third shell, contains a total of 10 electrons; higher in energy than s and p orbitals in the same shell.
vacancies
allow electrons to roam freely throughout the metal
delocalized
the electrons are said to be _______, if they do not belong to any one atom (sea of mobile elctrons)
Metallic bonding
Bonding between metals with electron pooling. Electrons are delocalized, moving freely throughout the entire piece of metal
Lewis Structure
_______ shows valence electrons
Lewis dot diagram
Diagram of an atom, ion or molecule in which each dot represents a valence electron
[Na]?
draw the lewis dot diagram of Na?
valence
lewis dot structures show _______ electrons
Draw the lewis dot diagram of F-
(F=7 valence e-, F-= 8 valence e-, don't forget the dots "8") [F]-
[Cs]?[Cs]?[(8-dots)S]²?
Draw the Lewis dot diagram of Cs2S
covalent bonds
atoms share pairs of electrons
bonding pair
an electron pair found in the space between two atoms
lone pair
a _______ (or non bonding electron air) occupies more apace than a bonding pair
Double covalent bond
a bond that involves two shared pairs of electrons
1
Simple Molecules Lewis Molecules rules:
three
Simple Molecules Lewis Molecules rules
two
number of groups to switch when showing an enantiomer
one
How many electrons does silver have to give up in order to achieve a pseudo-noble-gas electron configuration
???
Lewis Structures must account for all electrons!!! How many?
ionic, covalent and metallic bonds
what are the three types of chemical bonds?
metallic bond
a bond formed by the attraction between positively charged metal ions and the electrons around them
Lewis symbols
symbolic dots standing for valance electrons
Born-Haber
Determine the energy changes for ionic solid formation using a ---- cycle. Here we ue Hess's Law to calculate the lattice energy as the sum of several steps in the formation of an ionic compund
Single
A saturated compound has _______ bonds
double, triple
the sharing of two or three pairs of electrons between two atoms produces _______ or _______ bonds, respectively. double and triple bonds are examples of multiple bonding between atoms.
Bond polarity
In covalent bonds, the electrons may not necessarily be shared equally between two atoms. _______helps describe unequal sharing of electrons in the bond.
nonpolar covalent bond
a covalent bond in which the bonding electrons are equally attracted to both bonded atoms
polar covalent bond
a covalent bond in which a shared pair of electrons is held more closely by one of the atoms
electronegative
Fluorine is the most _______ element, meaning it has the greatest ability to attract electrons from other atoms.
0.7, 4.0
electronegativity values range from_______ for Cs to _______ for F.
increases, decreases
electronegativity generally _______ form left to right in a row of the periodic table, and _______ going down the column.
polarity
_______ of the bonds determines the polarity of the molecule
polar
a molecule in which the centroid of the positive charges is different from the centroid of the negative charges.
polar molecule
A _______ is one whose centers of positive and negative charge do not coincide. Thus, a polar molecule has a positive side and a negative side.
dipole (µ)
a pair of equal and opposite electric charges or magnetic poles separated by a small distance
Dipole moment
A measure of molecular polarity
covalent, ionic
most bonding interactions lie between the extremes of _______ and _______ bonding.
large
…when the oxidation state of the metal becomes __________.
Formal charge
(Valence electrons) - (# of bonds + # of electrons)
resonance structures
Sometimes a single Lewis structure is inadequate to represent a particular molecule (or ion). In such situations, we describe the molecule by using two or more _______ for the molecules.
odd number
The octet rule is not obeyed in three cases. (here is one): Exceptions occur when (a) a molecule has an _______ electrons,
distribution
The octet rule is not obeyed in three cases. (here is one): Exceptions occur when (b) it is nor possible to complete an octet around and atom without forcing an unfavorable _______ of electrons
bond enthalpy
energy required to break the bond
electrons pairs (shared between atoms.)
the strength of a covalent bond is measured by its bond enthalpy, which is the molar enthalpy change upon breaking a particular bond. How is the strengths of covalent bonds increased?
decreases, increases
the average bond length between two atoms decreases as the number of bonds between the atoms _______, consistent with the bond being stronger as the number of bonds increases.
E =(kQ1Q2)/d
potential energy of two interacting charges
µ=Qr
dipole moment
0
0
?H(rxn)=?(bond enthalpies of bonds broken)-?(bond enthalpies of bonds formed)
the enthalpy change as a function of bond enthalpies for reactions involving gas phase molecules
highest shell
were are valence electrons located located on a atom?
8
how many valence electrons could there be?
6 (remember outer most)
how many valence e- in O?
helium (He) 2 valence electrons
Which inert gas does not have a Lewis octet? How many valence electrons does it have?
H and Li
Which atoms and/or ions can achieve inert gas electron configurations without achieving Lewis octets? Name them.
F (fluorine)
which element has the highest electronegativity?
the more electronegative atom
were does the dipole moment always points towards?
1.60x10?¹? C
the charge on each atom is the electronic charge e=
debyes (D)
What unit are dipole moments measured in?
Debye
The unit used to express dipole moments. 3.34x10?³°
3.34x10?³°
what do debyes (D) units equal to
more
Slower reactions have _______ activation energy
reactants - products
bond energies. do you do reactants-products or products-reactants
what are the steps to calculate bond energies/enthalpies?
(first->balance equation.. second-> rewrite the balanced reaction using lewis structure.... last-> use enthalpies table and get the sum.