Midterm 2 Part A Flashcards
Chemical bonding: ___ that keeps atoms _____
Force
Together
3 types of chemical bonds
Ionic
Covalent
Metallic
Ionic Bonding: between a ___ and a ____. Involves a _____ of electrons
Metal
Nonmetal
Transfer
Ionic bonding: forms ____ structures , forms compounds that are ___,___,and brittle
Extended
Hard
Rigid
Ionic bonding: forms compounds that are poor _____ of heat and electricity in the ___ state
Conductors
Solid
Ionic bonding: forms good electrical conductors in the ___ or ____ phases
Molten
Aqueous
Ionic bonding: cation and anion are held together by attractive ______ forces given by Coulomb’s law
Electrostatic
E = (q1•q2)/d^2
What is lattice energy
Energy that is released when gaseous ions bond to form the ionic solid
What is lattic energy proportional to
And why is this important
The electrostatic force (E)
When looking at the trend for melting points of compounds we look at the size of the ions, and see the distance between them.
Larger distance= less lattice energy, meaning lower melting point
Lattice energy helps determine the _____ of the bond
Strength
If triangle H= (-770)J
What can we tell from this using the def of lattice energy
We need (-770)J to BREAK the ionic bond
Higher melting point requires _____(less/more) energy
More
What two things affect the melting point of a compound and why
Charges and distance between the atoms
These are the three variables on Coloumb’s law
Steps for determining melting point trends
1) look at charges
-elements in compounds with GREATER numerical charge have HIGHER melting point
2)if two compounds have elements of the same charge: look at atomic mass of elements in each compound
-greater atomic mass=larger distance between nucli= smaller LE=lower melting point
Covalent bonding: between a nonmetal and _____. Involves the sharing of _____.
Nonmetal
Electrons
Covalent bonding: forms compounds with _______structure as well as extended ______
Molecular
Structures
Covalent bonding: molecular compounds are typically gases or ____ with low melting or ____ points, whereas compounds with extended structures are ____ and rigid ____ with _____ melting points
Liquids
Boiling
Hard
Solids
High
What are the two types of covalent bonds and give an example of each
Pure covalent bonds (H2, O2, Cl2)
Polar covalent bonds (HF)
Pure covalent bonds have ____ sharing of electrons because of the SAME ___ of the bonded atoms
Equal
EA
Why do polar covalent bonds have an unequal sharing of electrons,
and which atom will draw electrons more strongly
Because the atoms have a difference in electro negativity
The atom with the HIGHER electronegativity will draw electrons more strongly
How can bond polarity be determined and what is the formula for this
Determined by calculating
triangle(EN)
triangle(EN)=| (En positive) - (En negative) |
Explain the difference between electron affinity and electronegativity
Electron affinity- referring to the ability of an ISOLATED atom in the GAS state to add an electron
Electronegativity- ability of an atom in a BOND to DRAW electron density
Metallic bonding: between a metal and a ___. Has an _____ structure of atoms in “sea” of ______ electrons
Metal
Extended
Delocalized
Metallic bonding: what does the sea of electrons do
Acts as a glue to keep the cations together
Metallic bonding: Metals are malleable and ____. They are good conductors of heat and _____. They have moderately _____ melting and boiling points.
Ductile
Electricity
High
What is a stable electron configuration
Valence electrons are distributed so that each atom has 8 electrons, 2 for hydrogen
Steps for drawing lewis structure for covalent bonds
1) determine the total # of ve
2) use pairs to join all atoms
3) distribute remaining electrons
4) if compound has a (-) or (+) charge MUST PUT SQUARE BRACKETS AROUND AND INDICATE CHARGE
Exceptions to the octet rule and why this happens
(What is this called)
Elements in period 3 and beyond can have 10 or 12 ve
Because they can use their d orbitals in bonding
(Expanded octet)
Incomplete octets: what does this mean and what elements are they
Elements may have LESS that 8 electrons
Beryllium, Boron, and aluminum
Odd electron species: what is it and how to deal with it
There could be one unpaired electron
This electron must be placed with the LEAST electronegative atom of the molecule
Formal charge: the difference between the # of ____ ___ in the free atom and the # of electrons _____ to the atom
Valence electrons
Assigned
Formal charge formula and what must you do to calculate this
FC on an atom= ve-(e in lone pairs)- (1/2)(e in covalent bonds/pairs)
Need to draw the Lewis structure to calculate formal charge on any element in the compound
All formal charges MUST __up to the overall ___ of the molecule
Add
Charge
Low formal charges are ___, FC of ___ is the most stable
Preferred
0
(+) formal charges are preferred on the ____ electronegative atom, and (-) FC’s are preferred on the ____ electronegative atom
Less
More
What is a resonant structure
Molecules that have MORE than 1 plausible Lewis structure. The true structure is then a resonance hybrid of all the contributing structures. Bonding electron density can therefore be delocalized over more than two atoms
What symbol represents a resonant structure
<—->
How to show a resonant structure
Insert picture of 03
Single bond has a bond order of ____
Double bond has a bond order of ___
1
2
In resonant structures all bonds are equivalent in ____ and _____
Length
Strength
Lower bond order= ___ and ____ bond
Higher bond order=___ and ____ bond
Weaker, longer
Stronger, shorter
What is the prediction of molecular shape based on
The EXTENT of REPULSION between two electron pairs
Lewis structures: electron pairs are arranged around the central atom to ____ repulsion
Minimize
of electron pairs around central atom?
Molecular shape: AX2
Shape?
Bond Angles?
2
Linear
2 bonding pairs
In the form AXE what do A, X, E represent?
A= central atom
X= terminal atom
E= lone pair
of electron pairs around central atom?
Molecular shape: AX3
Shape?
Bond Angles?
3
Trigonal planar
120 degrees bond angle
of electron pairs around central atom?
Molecular shape: AX2E
Shape?
Bond Angles?
3
Bent, angular, v shape
Less than 120, which is the ideal bond angle (because lone pair pushes on bonded pairs with more force)
Why are some bond angles smaller than the ideal bond angles
The presence of a lone pair
(Lone pairs occupy more space. They exert a stronger force of repulsion that a bonded pair)
of electron pairs around central atom?
Molecular shape: AX4
Shape?
Bond Angles?
4
Tetrahedral
109.5
of electron pairs around central atom?
Molecular shape: AX3E
Shape?
Bond Angles?
3 bonding, 1 lone
Trigonal pyramidal
Less than 109.5
of electron pairs around central atom?
Molecular shape: AX2E2
Shape?
Bond Angles?
2 bonding, 2 lone
Bent, angular
Less than 109.5
When labelling bond angles that are “less than” where do you always draw the arrow in between
2 bonding pairs
(Instead of a bonding pair and lone pair)
of electron pairs around central atom?
Molecular shape: AX5
Shape?
Bond Angles?
5 bonding
Trigonal bipyramidal
120 degrees
of electron pairs around central atom?
Molecular shape: AX4E
Shape?
Bond Angles?
4 bonding, 1 lone
See saw
Smaller than 120 and 90
of electron pairs around central atom?
Molecular shape: AX3E2
Shape?
Bond Angles?
3 bonding, 2 lone
T shape
Less than 90
of electron pairs around central atom?
Molecular shape: AX2E3
Shape?
Bond Angles?
2 bonding, 2 lone
Linear
180 degrees
of electron pairs around central atom?
Molecular shape: AX6
Shape?
Bond Angles?
6 bonding
Square pyramidal
90 degrees
of electron pairs around central atom?
Molecular shape: AX5E
Shape?
Bond Angles?
5 bonding, 1 lone
Square pyramidal
Less than 90 degrees
of electron pairs around central atom?
Molecular shape: AX4E2
Shape?
Bond Angles?
4 bonding, 2 lone
Square planar
90 degrees
What is electron group arrangement
Only considers how many THINGS the central atom is connected to (other atoms and lone pairs)
How to determine electron group arrangement shape
1) determine type (AXE thing)
2) add up the subscripts of X and E and March that number to the corresponding shape
linear= 2
trigonal planar= 3
Tetrahedral= 4
Trigonal bipyramidal= 5
Octahedral= 6
Valence Bond Theory: a _____bond is formed when atomic orbitals ______ and a pair of electrons is ______ in the region between the atoms
(The mixing of atomic orbitals to produce ____ orbitals)
Covalent
Overlap
Localized
Hybrid
Steps for using Valence Bond Theory
1) determine # of required hybrid orbitals
-look at # of effective pairs around central atom
2) determine hybrid orbital
-write condensed e-configuration of central atom
-look at last two energy levels to see which orbitals mix
-write hybrid orbital(superscript shows HOW MANY orbitals you took from that energy level)
What is a sigma bond between
Anything with p
What is a pi bond between
Only p-p
A sigma bond is the result of what kind of overlap?
Where is it electron density?
End-to-end overlap of orbitals
Has electron density along the axis of the bond
A pi bond is the result of what kind of overlap?
Where is it electron density?
Side-to-side overlap of orbitals
Has electron density BOTH above and below the axis of the bond
What is lattice energy
Energy released when anions and cations come together
Is bond formation and bond breaking exo or endothermic
Formation= exothermic
Breaking= endothermic
Bond strength is related to its ____ and ____
Length and energy
What does triangle H stand for
Enthalpy change
The shorter the bond, the ____ it is, therefore the ____ the bond energy
(And why)
Stronger
Higher
(Higher force of attraction)
Multiple bonds are STRONGER and have HIGHER bond energies why?
Because they’re shorter than single bonds
Do multiple or single bonds require more energy to break and why
Multiple bonds because they bring the atoms closer together
Molecular Orbital Theory: electrons are found in molecular orbitals which represent the _____ of electrons over the ____ molecule
(Crest molecular orbitals that contain ____ the electrons)
Delocalization
Entire
All
When writing condensed electron configuration of an ion (so has a charge) which orbital do you TAKE AWAY electrons from
(And give an example)
Take electrons out of the HIGHEST energy level (so highest numbered orbital)
Ex) take electrons out of the 4s before the 3d
Black line spectra: the last line after a big black block is always n= ____
Infinite
Black line spectra: what nf values do these correspond to?
Ground state
first excited state
Second excited state
n=1
n=2
n=3
Black line spectra: How to determine the n initial of the FIRST line
(And give an example)
First line always has a numerical difference of 1, so determine n final based on words give and add one
Ex) “second excite state” so n final=3
so n initial of the first line is 4
What is a metallic hydride
Hydrogen bonded to a TRANSITION METAL
What is an ionic hydride
Hydrogen bonded to an S-BLOCK element
What is a covalent hydride
Hydrogen bonded to a NON-METAL
When counting for condensed electron configuration do you INCLUDE the element that you want in you counting
YES
How to determine bond order in MO’s
Bond order=
(# of e on BMO- # of e on ABMO)/2
What property does stability correspond to and what does this mean
Bond order
Fractional bond order ISN’T stable
of molecular orbitals formed is always ____ to the # of atomic orbitals that are combined
Equal
The combination of ____ atomic orbitals gives one BMO and ___ ABMO
2
1
Bond order is a measure of ____ ____
Bond strength
What happens if bond order is 0
No bond exist, so atom isn’t formed
Trend in bond length:
Bond length increases= ____ bond = _____ BO
Weaker
Smaller
3 reasons why hydrogen is different from other elements of group 1
1) is a non metal
2) forms covalent bonds with non metals
3) forks ionic hydrides with metals and metallic hydrides with transition metals
What are H3O+ and OH- called
Hydronium and hydroxyl
What is an Arrhenius acid
(And what must it contain)
Compound that increases the concentration of H3O+ in solution
Must contain an ionizable H in the structure
What is an Arrhenius base
(And what must it contain)
Compound that increases the concentration of OH- ions in solution
Must contain an ionizable OH on the structure
What is a BL acid
Compound that can donate a proton (H+)
What is a BL base
A proton acceptor
What is a Lewis acid
(And what do they either have)
Compound that accepts an electron pair
Either have:
1) a polarized bond to hydrogen, so they lose a proton, H+
2) have empty orbitals into which they can accept electrons
What is a Lewis base to
Has atom(s) with non bonding electrons (lone pairs) which they can donate
A strong acid in water will ionize _______
A weak acid in water will ionize ______ (remember arrows)
Completely
Partially
HOW MANY VALENCE ELECTRONS DOES HYDROGEN HAVE when drawing lewis structures
1
