Chapter 10 Chemical Bonding I: The Lewis Model Flashcards
what does the lewis model emphasize?
valence electrons
Using Lewis model, we can draw chemical structures, called what?
Lewis structures
or
Electron dot structure
what does the Lewis structure allow us to predict?
molecular stability
shape
size
polarity
Chemical bonds form because they what between the charged particles that compose atoms.
lower the potential energy
when does a chemical bond form?
when the potential energy of the bonded atoms is less than the potential energy of the separate atoms.
When a metal atom loses electrons it becomes a WHAT?
Cation
When a nonmetal atom gains electrons it becomes an what
anion
what have high electron affinities?
nonmetals
what makes it advantageous to add electrons to atoms
high electron affinities
The oppositely charged ions are then attracted to each other, resulting in an
ionic bond
have a high ionization energy
nonmetals
when is the potential energy lowest?
when the electrons are between the nuclei
The simplest theory of metallic bonding
metal atoms releasing their valence electrons to be shared as a pool by all
where does metallic bonding result from?
attraction of the cations for the delocalized electrons.
involves the transfer or sharing of valence electrons between two or more atoms.
chemical bonding
are most important in bonding.
valence electrons
indicates the number of valence electrons for main group elements.
column number on the periodic table
how many electrons do transition elements have?
2
how to represent valence electrons of main group electrons in the lewis structure?
dots surrounding the symbol for the element.
We use the what to represent nucleus and inner electrons.
symbol of the element
When atoms bond, they tend to gain, lose, or share electrons to result in eight valence electrons
Octet Rule `
exceptions to octet rule
H
Li
Be
B
having two valence electrons
a duet
is the arrangement of cations and anions in a crystalline structure
crystal lattice
long-range repeating order of the ions).
crystalline
what is a crystal lattice held by?
the electrostatic
attraction of the cations for all the surrounding anions.
The extra stability that accompanies the formation of the
crystal lattice is measured as the what?
lattice energy
the energy released when the
solid crystal forms from separate ions in the gas state.
lattice energy
what does lattice energy depend directly on
size of charges
what does lattice energy depend indirectly on
distance between ions
is a hypothetical series of reactions that represents the formation of an ionic compound from its constituent elements.
Born-Haber Cycle
The force of attraction between oppositely charged particles is directly proportional to what?
the product of the charges
Larger charge the what the attraction
stronger
the strong the attraction the what the Lattice energy
more
all ionic compounds are what at room temp?
SOLID
what kind of attraction is nondirectional
electrostatic attraction
predicts ionic compounds should have high melting points and boiling points because breaking down the crystal should require a lot of energy.
Lewis theory
the stronger the attraction, the what the melting point?
the higher
is measured by rubbing two materials together and seeing which “streaks” or cuts the other.
hardness
The harder material is the one that what?
cuts or doesn’t streak
To conduct electricity, a material must have what?
charged particles that are able to flow through the material.
Lewis theory predicts that ionic solids should not conduct what?
electricity
what should conduct electricity
liquid ionic compound
and
ionic compound dissolved in water
The sharing of valence electrons is called
covalent bonding
Electrons that are shared by atoms are called
bonding pairs
Electrons that are not shared by atoms but belong to a particular atom are called
lone pairs
or nonbonding pairs
When two atoms share one pair of electrons, it
is called a
single covalent bond
When two atoms share two pairs of electrons the result is called a
double covalent bond
When two atoms share three pairs of electrons the result is called a
triple covalent bond.
Lewis theory of covalent bonding implies that the attractions between atoms are
directional
Lewis theory predicts covalently bonded compounds will be found as what?
individual molecules
Lewis theory predicts that the melting and boiling points of molecular compounds should be
low
what bonds are strong and what attraction is weak
covalent
attractions
Lewis theory predicts that the hardness and brittleness of molecular compounds should vary depending on the
strength of intermolecular attractive forces.
most of the molecular solids are what?
soft and waxy
should the molecular solids conduct electricity?
no
should the molecular liquids conduct electricity?
no
what conducts electricity when dissolved in water?
Molecular acids
Lewis theory predicts that the more electrons two atoms share, the what the bond should be.
stronger and shorter
is measured by how much energy must be added to break the bond.
bond strength
is determined by measuring the distance between the nuclei of bonded atoms
bond length
Covalent bonding between different types of atoms results in
unequal sharing of electrons.
unequal sharing of electrons.
polar covalent bond
bond polarity
The end with the larger electron density gets a what?
a partial negative
The end that is electron deficient gets a
a partical positive charge
The charged ends of the molecule represent a
dipole
is a measure of bond polarity.
dipole moment
is a material with a + and − end.
dipole
Generally, the more electrons two atoms share and the larger the atoms, the what the dipole moment.
larger
The ability of an atom to attract bonding electrons to itself is called
electronegativity
is the most electronegative element.
fluorine
is the least electronegative element.
francium
are not assigned values.
noble gas atoms
The larger the difference in electronegativity, the what the bond.
more polar
If the difference in electronegativity between bonded atoms is what the bond is pure covalent.
0
If the difference in electronegativity between bonded atoms is what the bond is nonpolar covalent
0.1 to 0.4
If the difference in electronegativity between bonded atoms is what the bond is polar covalent
0.5 to 1.9
If the difference in electronegativity between bonded atoms is what the bond is ionic
larger than or equal to 2.0
is the percentage of a bond’s measured dipole moment compared to what it would be if the electrons were completely transferred.
percent ionic character
The percent ionic character indicates the degree to which the electron is what?
transferred
Elements with empty d orbitals can have more than eight electrons.
expanded octets
Delocalization of charge helps to what?
stabilize the molecule
When there is more than one Lewis structure for a molecule that differ only in the position of the electrons, they are called
resonance structures
The actual molecule is a combination of the resonance forms a what?
resonance hybrid
is a fictitious charge assigned to each atom in a Lewis structure that helps us to distinguish among competing Lewis structures.
formal charge
most stable structures have what?
– Fewer formal charges.
– Smaller formal charges.
– Negative formal charges on the more electronegative atom.
Chemical reactions involve breaking bonds in reactant molecules and making new bonds to create the products.
bond energies
The amount of energy it takes to break one mole of a bond in a compound is called the
bond energy
each atom gets 1⁄2 bonding electrons
Homolytic Cleavage
electrons are unequally divided
Heterolytic Cleavage
actual bond energy depends on what?
the
surrounding atoms and other factors.
The distance between the nuclei of bonded atoms is called the
bond length
involves the metal atoms releasing their valence electrons to be shared by all atoms/ions in the metal.
The simplest theory of metallic bonding
As temperature increases, the electrical conductivity of metals
decreases
