Exam 1 Flashcards
What is avogadro’s number?
6.022 x 10^23
What is the conversion from Celsius to Kelvin?
K = degrees C + 273.15
In terms of grams, how much are megagrams?
1 x 10^6 (1,000,00)
In terms of grams, how much are micrograms?
1 x 10^-6 (0.000001)
What is the formula for density?
d = m/v (mass/volume)
What is a mixture?
A physical combination of two or more substances
What are the two types of mixtures?
Hetergeneous and homogeneous
What is a compound?
A substance composed of two or more elements that are chemically united in fixed proportions
How can a mixture be separated?
Through physical means
How can a compound be separated?
Through chemical means
What is accuracy?
How close a measurement is to its true value
What is precision?
How closely multiple measures are to to one another
What are isotopes?
Atoms of an element with the same number of protons but different number of neutrons
What does the quantum mechanical model describe?
It describes the energy of an electron in atom
What is the Heseinberg Uncertainty Principle?
It is impossible to know both the position and momentum of a particle with certainty
What is a shell?
Example: 1s or 2s2p or 3s3p3d
What is a subshell?
Example: 2s or 2p or 3d
What is an orbital?
Example: 2s has two orbitals or 2p has three orbitals
What is the principle quantum number?
It determines the size (n=0,1,2…)
What is the angular momentum quantum number?
It determines the shape and volume (l=0,1,2…)
What is the magnetic quantum number?
It determines which orbital an electron is in (ml=-2,-1,0,1,2…)
What is the shape of the s orbital?
Spherical
What is the shape of the p orbitals?
Dumbbell
What is the shape of the d orbitals?
4-leaf clovers
How many orbitals are in the s, p, d, and f orbitals?
s: 1 orbitals
p: 3 orbitals
d: 5 orbitals
f: 7 orbitals
What is the electron spin quantum number?
Determines the spin of an electron (ms=-1/2,1/2)
What is the Pauli Exclusion Principle?
No electron in an atom can have the same four quantum numbers
How many electrons can an orbital hold?
2 electrons
What orbital do these quantum numbers represent:
n=1
l=0
ml=0
s orbital
What orbital do these quantum numbers represent:
n=2
l=1
ml=-1,0,1
p orbital
What orbitals do these quantum numbers represent:
n=3
l=2
ml=-2,-1,0,1,2
d orbital
What orbitals do these quantum numbers represent:
n=4
l=3
ml=-3,-2,-1,0,1,2,3
f orbital
What are degenerate orbitals?
Orbitals with the same energy level
What is the relationship between how close an electron can get to the nucleus and the amount of energy it has?
The closer an electron can get to the nucleus, the more stable it is, and the lower the energy it has
What is the Hund’s Rule?
In a set of degenerate orbitals, the number of unpaired electrons with the same spin is maximized
What are exceptions to electron configuration?
Chromium: greater stability with a half-filled 3d subshell
Copper: greater stability with a fully-filled 3d subshell
What is shielding?
Inner electrons block outer electrons from nuclear charge
What is nuclear charge?
The positive charge present in the nucleus of an atom
What is effective nuclear charge?
The nuclear charge an electron actually experiences
What is the trend for effective nuclear charge?
It increases across the period and down the group
Why does effective nuclear charge increase across the period?
The number of core electrons stays the same as the number of protons and valence electrons increase
Why does effective nuclear charge increase down the group?
It increases less significantly than across the period because it is offset by the increase in core electrons
What is atomic radius?
The distance between the nucleus of an atom and its valence shells
What is the trend for atomic radius?
It decreases across the period and increases down the group
Why does atomic radius decrease across the period?
Effective nuclear charge increases across the period therefore those valence electrons are experiencing more of the nucleus’ pull and thus pulled closer
Why does atomic radius increase down the group?
The principle quantum number increases down the group which means there is a whole new set of core electrons
What is ionization energy?
The energy required to remove an electron from a gaseous atom
What is the trend for ionization energy?
It increases across the period and decreases down the group
Why does ionization energy increase across the period?
Electrons are pulled more tightly to the nucleus of an atom as you go across the period, making it harder to remove said electrons
Why does ionization energy decrease down the group?
It is easier to remove the valence electrons from bigger atoms because they are so far away from the nucleus
What do atoms with low IE tend to form?
Cations (positively charged ions)
What do atoms with high IE tend to form?
Anions (negatively charged ions)
What IE do noble gases have?
Very high IE because they do not want to ionize
What the exceptions in the IE trend?
Nitrogen has a higher IE than oxygen because oxygen has one set of paired electrons in its 2p orbital, which means there are more electron-electron repulsions, making it easier to remove one of the electrons in the pair. Beryllium has a higher IE than boron because boron has one electron in its p orbital and because the p orbital is further away from the nucleus, it is easier to remove it.
What is the relationship between first ionization energy and second ionization energy?
In second ionization energy, it becomes more difficult to remove another electron.
How much energy does it require to remove a core electron?
It requires a large amount of energy because those core electrons are closer to the nucleus and will experience a greater effective nuclear charge
What is electron affinity?
The negative (-1x) of the energy change that occurs when an electron is accepted by an atom in the gaseous state
What is the favorable value for electron affinity?
Large and positive values
What do atoms with low EA tend to form?
Cations
What do atoms with high EA tend to form?
Anions
What is the trend for electron affinity?
It increases across the period and decreases down the group
Why does electron affinity increase across the period?
Since effective nuclear charge increases across the period, an electron can be more easily added because it will feel more of the nuclear’s charge (also the atoms to the right of the periodic table want to gain a noble gas configuration)
Why does electron affinity decrease down the group?
The atoms are much bigger and therefore will not experience that much of the nuclear’s charge and will instead want to remove an electron, not add one
What is an exception to EA trend (F)?
Cl has a greater EA than F because it Cl is bigger than F and has a bit more space to add an electron
What is an exception to EA trend (Group 2)?
Group 1 has higher EA than group 2 because it is easier to add an electron to an s orbital rather than a p oribital
What is an exception to EA trend (Group 5)?
Group 4 has a higher EA than group 5 because within the p subshell, it is easier to add an electron to an empty orbital than to add one to an orbital that already contains an electron
What is the trend for metallic behavior?
It decreases across the period and increases down the group
When a cation is formed, which electron is removed first?
The electron is removed first from the highest value of ns orbital and then from the (n-1)d orbitals; for example, remove from 4s first than from 3d
What does isoelectronic mean?
An ion with the same electron configuration as a noble gas
What is ionic radius?
The radius of a cation or anion
Are cations bigger or smaller than their ground state atoms?
Cations are smaller because there are less electrons meaning there are more protons pulling the remaining electrons closer to the nucleus
Are anions bigger or smaller than their ground state atoms?
Anions are bigger because more electrons leads to electron-electron repulsion
Is an compound used for ionic or covalent bonds?
A compound can be either ionic or covalent
What is a molecule?
The basic unit of an element or compound, consisting of two or more atoms bonded by the sharing of electrons
What is an ionic compound?
A pure substance that is formed from a metal and a nonmetal that has an overall neutral charge
What is a diatomic molecule?
A molecule that contains two atoms and may be heteronuclear or homonuclear
What is a polyatomic molecule?
A molecule that contains two or more atoms
What does the Law of Conservation of Mass state?
Mass is constant during ordinary chemical reactions and atoms present before the reaction also must be present after
What does the Law of Multiple Proportions state?
Some elements can combine with each other in different whole number proportions, but you cannot have a fraction of an atom
What is the formula for percent composition by mass?
(mole x molecular weight) / (molecular weight of compound) x 100
What is empirical formula?
A compound that agrees with the elemental analysis and gives rise to the smallest set of whole numbers of atoms
What is molecular formula?
The formula of the compound as it exists (may be a multiple of the empirical formula)
What are chemical bonds?
The force of attraction between any two atoms in a compound. Lowers potential energy.
What are ionic bonds?
The transfer of electrons between a metal and nonmetal in which ions are held together by electrostatic force of opposite charges
What are reactive metals?
The metals with a low IE and low EA and that have the tendency to form cations
What are reactive nonmetals?
The nonmetals with a high IE and high EA and that have the tendency to form anions
What is a lattice?
Cations surrounded by anions and anions surrounded by cations which maximizes attraction between ions
What is lattice energy?
The measure of the strength of bonds in an ionic compound
What are physical properties of ionic compounds?
Dissolve in water and conduct electricity
What is the relationship between charge, attraction, and lattice energy?
Larger charge = stronger attraction = larger lattice energy
What is the relationship between ion size, attraction, and lattice energy?
Larger ion = weaker attraction = smaller lattice energy
When determining lattice energy, is size or charge more important?
Charge
What is Coulomb’s Law?
F = k((Q1Q2)/d^2)
What is metallic bonding?
The electron pooling between two metals
What is the electron “sea”?
All metal atoms in a sample contribute their valence electrons to a form a delocalized electron “sea”
What is the octet rule?
Atoms will lose, gain, or share electrons in order to achieve a noble gas configuration
What is bond order?
The number of electron pairs being shared by a given pair of atoms
What is bond energy?
The energy needed to overcome the attraction between nuclei and shared electrons
What is bond length?
The distance between the nuclei of two covalently bonded atoms
In terms of bond length, what are the lengths of single, double, and triple bonds?
Triple > double > single
What is the trend for bond length?
It decreases across the period and increases down the group
What is the relationship between bond order, length, and energy?
Higher bond order = shorter bond length = higher bond energy
What is electronegativity?
The measure of ability of an atom in a compound to draw electrons to itself in a bond
Which element is the most electronegative?
Fluorine
What is the trend for electronegativity?
It increases across the period and decreases down the group
What is electronegativity values for a nonpolar covalent, polar covalent, and ionic bond?
0 < EN < 0.5 (nonpolar)
0.5 < EN < 2 (polar)
EN > 2 (ionic)
What is dipole moment?
The measure of a bond’s polarity within a molecule
What are the common bonding patterns for C, N, O, H, Be, and B?
C: 4 bonds, 0 lone pairs
N: 3 bonds, 1 lone pair
O: 2 bonds, 2 lone pairs
H: 1 bond
Be: 2 bonds, 0 lone pairs
B: 3 bonds, 0 lone pairs
What is a functional group?
The reactive portion of a molecule
What are the properties of a functional group?
They are often polar, double (or triple) bonded, and act as acids and bases
How do you calculate formal charge?
= valence electrons - (lone electrons + 0.5(bonded electrons))
What is a resonance structure?
When more than one Lewis structure for a molecule is valid
What is a resonance hybrid?
The actual molecule is an average of the resonance forms
What is electron delocalization in covalent bonds?
In resonance structures, electrons are delocalized: their density is “spread” over a few adjacent atoms (use dotted lines to show this)
Are all resonance structures equal?
No, one may contribute more to the resemblance of the actual molecule more than the others
How do you use formal charge to choose best resonance structure?
Structures must (in 2nd row) satisfy the octet rule.
Atoms with formal charges should be in agreement with EN trends.
Structures with +/- 2 are unimportant.
Structures with two like charges on adjacent atoms are not favorable.
Formal charges add up to total charge of compound.
What are isomers?
Have the same molecular formula but different bonding between atoms
What is the difference between isomers and resonance structures?
Isomers are different molecules with same molecular formula while resonance structures are the same molecule but each structure differs in the position of electrons
What is a peptide bond?
A covalent bond that joins together the carboxyl group and the amino group of another amino acid
What is another name for a peptide bond?
Amide bond
Why is the peptide bond planar?
The resonance structures result in a partial double bond that restricts rotation around the central C-N bond
Why is the restricted rotation in proteins important?
It greatly influences protein structure
What is a free radical?
An odd number of electrons (very reactive)
What is an expanded octet?
The central atom has more than eight electrons
Which elements have an expanded octet?
Elements in period 3 and beyond
Why can elements have an expanded octet?
They have empty d orbitals that can accommodate extra valence electrons
Why do expanded octets occur (what is the goal of them)?
To minimize formal charges
What are common bonding patterns for P, S, and Cl
P: forms 3, 4, or 5 bonds
S: forms 3, 4, or 6 bonds
Cl: forms 3, 4, 5, or 7 bonds
Find molecular geometry and bond angle:
2 electron domains
0 lone pairs
Linear
180 degrees
Find molecular geometry and bond angle:
3 electron domains
0 lone pair
Trigonal Planar
120 degrees
Find molecular geometry and bond angle:
3 electron domains
1 lone pair
Bent
118 degrees
Find molecular geometry and bond angle:
4 electron domains
0 lone pairs
Tetrahedral
109.5 degrees
Find molecular geometry and bond angle:
4 electron domains
1 lone pair
Trigonal Pyramidal
107.5 degrees
Find molecular geometry and bond angle:
4 electron domains
2 lone pairs
Bent
104.5 degrees
Find molecular geometry and bond angle:
5 electron domains
0 lone pairs
Trigonal Bipyramidal
90 degrees (axial)
120 degrees (equatorial)
Find molecular geometry and bond angle:
6 electron domains
0 lone pairs
Octahedral
90 degrees
What is VSPER?
Valence Shell Pair Electron Repulsion Theory that is used to predict the shape of molecules
What is an electron domain?
Any number of electrons that occupy a localized region around an atom
Why are electrons trying to arrange themselves as far apart as possible?
Electrons repel each other
What is electron domain geometry?
The arrangement of electron domains around the central atom, including both bonding and non-bonding electrons
What is molecular geometry?
Arrangement of bonded atoms
What is bond angle?
Angle between two adjacent bonds
What is true about lone pairs and multiple bonds when it comes to bond angle?
Lone pairs take up more space than bonding electrons and multiple bonds repel more than single bonds
What must be true for a molecule to be polar?
It must have polar bond and an asymmetrical shape
What are the common shapes and patterns of a nonpolar molecule?
It has a linear, trigonal planar, or tetrahedral shape and all the outer atoms are the same
What is the valence bond theory?
A covalent bond forms when the orbitals of the two atoms overlap and a pair of electrons occupy the overlap region
What is the three things that must be true for the valence bond theory?
A bond forms when singly occupied atomic orbitals on two atoms overlap.
Two electrons shared in the region of orbital overlap must be of opposite sign.
The formation of bond results in a lower potential energy for the system.
What is the relationship between overlap and strength in the valence bond theory?
The greater the overlap = the greater the strength
What is hybridization?
Atomic orbitals “mix” or hybridize when bonding occurs to form hybrid orbitals - a new set of degenerate orbitals
What determines hybridization?
Determined by geometry
What must be true for the number of hybrid orbitals formed and number of atomic orbitals mixed?
Number of hybrid orbitals formed = number of atomic orbitals mixed
Which atoms cannot hybridize?
Hydrogen
What is the hybridization when there are two electron domains?
sp
What is the hybridization when there are three electron domains?
sp2
What is the hybridization when there are four electron domains?
sp3
What is the hybridization when there are five electron domains?
sp3d
What is the hybridization when there are six electron domains?
sp3d2
What is the relationship between absorbance and concentration?
Directly related; as absorbance increases, concentration also increases
Why is it important to set the wavelength of the spectrophotometer before measuring the absorbance of the solutions?
At this particular wavelength, changes in concentration affect changes in absorbance the most
What is the purpose of making a standard curve?
Creating a standard curve allows us to approximate values of absorbance or concentration when we only have one known
How do you calculate Rf factor?
Distance traveled by component / Distance traveled by solvent
What are amino acids?
The monomers that make up proteins
How many unique amino acids are?
20
What is thin layer chromatography used for?
Used to separate the components of a mixture
What are the two phases of TLC?
Stationary and mobile phase
What is the Bradford Assay used for?
To measure the amount, or concentration, of a protein of an unknown solution
What does a dark blue color in a Bradford Assay mean?
The darker the blue, the more protein concentration is in a solution
What type of chemical reaction occurs during a Tollens’ Test?
The oxidation of sugar and reduction of silver ions to metallic silver
What is the Tollens’ Test used for?
Used to distinguish between aldehydes and ketones
What does it mean when the test tube becomes a silver mirror during a Tollens’ Test
It means that it is an aldehyde
How do you calculate percent error?
(actual - theoretical)/theoretical x 100
How do you calculate percent recovery?
mass of fat recovered/theoretical mass of fat x 100
How does adding 2-propanol to the chips allow you to extract the fat while leaving behind other components of the chips?
Lipids are soluble in 2-propanol because both are non polar. Since solubility is based on polarity, carbohydrates and other potato chip components such as water are polar and will not dissolve in the non polar 2-propanol.
Why is it easier to remove the fat from the original Ruffles than the baked?
The original Ruffles has a more fat content than the baked, therefore, there is more to be extracted during the lab
What structural characteristics gives us the ability to spool the DNA?
DNA is actually very long so when we isolated the strawberry’s DNA, it allowed us to easily spool the DNA. Plus, DNA is polar similar to the glass rod, so they are attracted to each other
What was the purpose of adding salt to the homogenization solution (strawberry)?
Salt helps break down the cell walls and membranes to get the DNA that lies inside the nuclei. It also denatures and precipitates the proteins in the strawberry cell
