chapter 3: Bonding general concepts Flashcards
what is chemical bonding?
the potential energy of the bonded atoms is less than the potential energy of separate atoms
what are some electrostatic interactions in bonds
the attraction between electron and nuclei, repulsions between electrons, repulsions between nuclei
what are the types of chemical bonds
metal to nonmetals, nonmetal to nonmetal, metal to metal
what is a metal to nonmetal bond called
ionic bond
what is a nonmetal to nonmetal bond
covalent bond
what is a metal to metal bond
metallic bond
what is a chemical formula
composition of a substance
what are the 3 types of chemical formulas
empirical formula, molecular, structural
what is the empirical formula
the lowest whole number ratio of atoms
what is a molecular formula
give the exact number of the atoms
what is a structural formula
sketch or diagram of how the atoms in a molecule are bonded together
what is a molecular model
the more accurate and complete way to specify a compound
what do a ball and stick model represent?
chemical bonds, balls are color-coded for specific elements
what is constructive interference?
waves interact to make a longer wave
what is destructive interference?
waves interact to cancel each other
what did the pauli exclusion state
no 2 electrons in the same atom can make the same energy and no orbital can have more than 2 electrons, and can’t have the same spin
what was hund’s rule
every orbital in a subshell is singly occupied with one electron before any one orbital is doubly occupied,
what is the aufbau principle
electrons fill from the lowest energy first
what is an example of a ionic bond
NaCl
what is an example of a covalent bond
H2O
what is an example of a metallic bond
Na+
what is a chemical formula
composition of a substance
what are the three types of chemical formulas
empirical, molecular, structural
what is an empirical formula
gives the lowest whole number ration of atoms
what is a molecular formula
molecular formula gives the exact # of atoms of each element in the compound
what is a structural formula
sketch of graph of how the atoms ina molecule are bonded together
what is a molecular model
more accurate and complete way to specify a compound
what is a ball and stick model
balls and sticks represent the chemical bonds
balls = atoms
sticks= bond
what is a space filling molecular model
atoms fill in the space between each more closely to represent an estimate of how a molecule might appear
how is an ionic bond formed
when oppsitely charged ions attract each other
what is another name for ionic bond
ionic compound
what is an ionic compound composed of in a sold state
lattice
what is a lattice
3D array of alternating cations and anions
does a lattice have low or high potential energy
low
what is the principle of coulomb’s law
ionic compounds are stable bc of the attraction between ions and unlike charges
what does coulomb’s law state
longer distance = less attraction; shorter distance = more attraction
higher charge = stronger force= larger lattice energy
what is coulomb’s formula
k (Q1Q2/r^2) = F
what does k represent in coulombs
coulomb’s constant; 2.13x10^-19 nm
what does r^2 represent
the distance
if the distance is larger than the charge then there is not a lot of force or energy
what are some properties of ionic compounds
high melting points and boiling points
solids are brittle and hard
why does it take a lot of energy to breakdown the crystal lattice
attractions between ions are strong
stronger attracton = higher melting point
why is the position of the ion in the crystal important
where the attractive forces are
what happens when you displace ionss
charges come closer together
what do covalently bounded atoms make
a molecule
what is another name for a covalent bond
molecular compound
what is bond length
equilibrium distance between the nuclei of two groups or atoms that are bonded to each other.
what are some properties of covalent bonds
○ Low melting and boiling points
○ Found in all 3 states at room temperature
○ Breaks attractions between molecules but not the bond
○ Strong covalent bonds within the molecules, weaker intermolecular between molecules
what is a polar covalent bond
Covalent bond where electrons are not shared equally
When will a molecule have more electron density?
When one electronegative atom pulls harder on an atom that is lower in electronegativity ( the one with high electronegativity is denser)
What is electronegativity?
Ability of atoms in a molecule to attract electrons to themselves
What is the electronegativity trend for the periodic table
○ Decreases down a group
○ Increases across a period
What is the most electronegative atom
fluorine
• Who founded the method for determining electronegativity?
linus pauling ( won Nobel prize for chemistry and peace)
What does a larger difference in electronegativity equal?
more polar bond
how are the bond length and electronegativity related
○shorter bond length = high electronegativity difference (strong bond bc the further away two atoms are then it’s stronger)
○longer bond length = low electronegativity difference (weaker)
What does electronegativity have to be to have a non-polar covalent bond?
0-0.4
What does the electronegativity difference have to be to be a polar bond
0.5-1.9
What happens if the electronegativity difference is larger than or equal to 2.0
ionic bond
what does ion size depend on
nuclear charge # of electrons orbitals in which the electrons reside
what does a higher effective nuclear charge mean
A higher effective nuclear charge causes greater attractions to the electrons, pulling the electron cloud closer to the nucleus which results in a smaller atomic radius.
what type of ion is smaller than the parent
cation
what type of ion is larger than the parent ion
anion
how does ion size increase
go down a column bc of the increasing n value
what is an isoelectronic series
ions have the same # of electrons
In an isoelectronic series, why is it that the ion w/ the highest charge is the smallest
○ Bc the nucleus exerts a stronger force of attraction and the electrons are pulled closer to the nucleus
cation with the highest postive charge has what radius
smallest radius
anion with the highest negative charge has what size radius
largest radius
what do more protons mean
greater positive charge = small radius
what do fewer protons mean
greater negative charge = large radius
what is the trend for atomic radius
decreases from left to right
increases down a group
how can you determine the formulas of ionic compounds
charge on cation = subscript of anion
charge on anion = subscript of anion
what is the percent ionic character
no bond is 100% between discrete pairs of atoms
what do models help with
explain how nature operates on a microscopic level based on experiences in the macroscopic workd
why can models be wrong
oversimplified
what is a bonding model?
the model that explains the stability of molecules
what is the localized electron bonding model
lewis structure; assumes that a molecule is composed of atoms that are bound together by sharing electrons using the orbitals
what are lone pairs
electrons that are not paried
what is the LE model composed of
- description of the VE arrangement in a molecule
- prediction of the geometry of the molecule using the vsepr model
- description of the type of orbitals used by the atoms
who were lewis structures named after
G.N lewis
what are valence electrons
outer shell electrons that are involved in chemical bonding
what are core electrons
inner shell electrons
What is the octet rule?
○ When atoms bond they gain, lose, or share electrons to have 8 valence electrons
○ 8 valence electrons are stable
What does more stable atom mean?
Lower potential energy
What do chemical reactions involve?
○ Breaking bonds in reactant molecules and making new bonds to create products
What is the strength of a bond measured by?
○ How much energy is required to break the bond (bond energy)
What happens when atoms share more electrons
the bond is stronger
What does a shorter bond mean
The bond is stronger
Why do we use the average bond length
○ Actual bond length depends on other atoms; we use the avg for similar bonds from many compounds
what are the bond length trends
increases down a group (the principal number increases )
bond length decreaes left to right across a period bc getting farther away from the nucleus
What is formal charge
The charge it would have if all of the bonding electrons were shared equally between the bonded atoms
• What is the formal charge formula
Formal charge = # of valence electrons - # of dots in the pairs- # of bonds it sees
• What determines the best Lewis structure
○ One w/ the fewest charges
Puts a negative charge on the most electronegative
What are resonance structures used for?
used to describe multiple structures of a molecule
What does a resonance structure differ in
The position of electrons
• What are the exceptions to the octet rule?
○ Ions or molecules w/ an odd number of electrons
○ Ions or molecules w/ less than an octet
○ Ions or molecules w/ more than 8 ve
What are odd number of electrons called
radicals
what is chemical nomenclature
system that us used to name substances w/ common names
how do you name ionic compounds/ bonds
name of cation metal = base name of anion nonmetal (ide)
ex. Nacl = sodium chloride
what is a multivalent cation
metal with multiple charges
how to name a multivalent cation
name of cation metal ( charge of cation in roman numeral in () ) base name of anion + ide
what does more oxygen =
ate
what does less oxygen =
ite
how many oxygens do central atoms on the second row have
3
how many oxygens do central atoms on the third row have
4
in polyatomic ions when does the charge increase
when you go from left to right
what is the rule for ammonium?
ammonium with a non metal ends in ide
how to name molecular compounds / covalent compounds
prefix + name of 1st element + prefix + base element of second element + ide
example: NI3 = nitrogen triiodide
what is does mono mean
1
what does di- mean
2
what does tri- mean
3
what does tetra- mean
4
what does penta-mean
5
what does hexa- mean
6
what does hepta- mean
7
what does octa mean
8
what does nona mean
9
what does deca mean
10
what are binary acids and what is the formula
contain only 2 different elements and their names
hydro + base name of nonmetal ic + acid
example: HF = hydrofluoric acid
how to name oxyacids
polyatomic ion ends in ate = ic and acid
example: HNo3 = nitric acid
if it ends in ite = ous
chlorite = chlorous acid
