Chem 101- Exam 1 Review
define and trend of ionization energy
-amount of energy necessary to remove an electron from a species -increase as we move across a period -decreases as we move down a group (family). -s and p block elements have larger range of IE, d and f block elements increase more slowly as we move from left to right.
define and trend in atomic radii
-based on distance between nuclei when they are bonded together increases down a group, decreases across a period
Change in energy states for absorption and emission of a photon in a hydrogen atom.
-electron must absorb energy in order to move to a higher-energy state (higher value of n). Radiant energy is emitted when the electron jumps to a lower-energy state (lower value of n). *The energy of the photon (E photon) must equal the difference in energy between the two states (▲E). The sign of ▲E tells us whether the photon is absorbed or emitted: when ▲E is positive, a photon must be absorbed as the electron jumps to a higher energy when ▲E is negative, a photon is emitted as the electron falls to a lower energy level.
define and describe trend in electron affinity
-energy associated with adding an e- to a species (almost always negative) ***not reverse of ionization energy*** -increasing e- affinity as you move across -decreases going down a group
Explain how the value of Delta E or Delta H relates to the stoichiometry in a thermochemical equation, and more specifically the effect on Delta E or Delta H of changing the stoichiometric coefficients by a constant factor or by reversing the chemical equation
-magnitude of ▲H is proportional to the amount fo reactant consumed in the process (proportional to the coefficient in equations). -when reversing a reaction we flip the sign of the ▲H or ▲E.
Explain how basic chemical properties of atoms, such as whether they are metallic or non- metallic, or the reactivity of a series of metals in water, can be explained in terms of the their electronic configurations and the underlying trends in electronic configurations and orbital properties.
-metals tend to have low ionization energies and therefore tend to from cautious relatively easily -first ionization energy is the best indicator of whether an element behaves as a metal or a nonmetal
Use the mathematical definition of the enthalpy H to relate Delta E and Delta H
H= E +PV E (internal energy), P (pressure), and V (volume)
Define heat and heat capacity, and perform calculations that interrelate heat, heat capacity, and temperature changes; define the specific heat capacity and the molar heat capacity and use them in calculations involving heat and temperature changes
Heat- is energy used to cause the temperature of an object to increase. heat capacity- the quantity of heat required to raise the temperature of a sample of matter by 1 degrees C or 1 K specific heat- the heat capacity of 1 g of a substance; the heat required to raise the temperature of 1 g of a substance by 1 degrees C. molar heat capacity- heat required to raise the temperature of one mole of a substance by 1 degrees C. specific heat (specific heat capacity)- heat capacity of one gram of a substance q=m(s)(change in temperature)
Explain Hess's Law, and use it to determine the enthalpy change for a given reaction from the enthalpies of reaction for a series of other reactions involving the same chemical species
Hess's law: if a reaction is carried out in a series of steps, ▲H for the overall reaction equals the sum of the enthalpy changes for the individual steps. sum the equations or their reserves and multiplying each by an appropriate coefficient so that they add to give the net equation for the reaction of interest.
Define and compare different types of energy, e.g. kinetic, potential, and thermal
Kinetic- Energy of motion, related to the mass and speed of object E=.5mv^2 Potential- stored/position energy Thermal- energy that is generated and measured by heat. (ex: kinetic energy of an atom or chemical energy in a molecule)
isoelectronic series
a series of atoms, ions, or molecules having the same number of electrons as we move down a group, ions carrying same charge are increasing in size. ex. O^2-, F-, Ne, Na+, Mg2+, Al3+ all have 10e- O2- largest, Al3+ smallest
why are energies of the various subshells in a given shell are different?
because of electron-electron repulsion -In a many-electron atom, for a given value of n, the energy of an orbital increases with increasing value of 1.. -in a hydrogen atom the energy of an orbital depends only on its principal quantum number, n. -3s, 2p, and 3d sub shells all have the same energy
trend in ionic radii
cations (+ charge)- are smaller than parent atom Na+< Na anions (- charge) are larger than parent atom Cl->Cl as we move down a group, ions carrying same charge are increasing in size.
Define (and give examples or compare where relevant) the following terminology: closed
closed- exchange energy but not matter with surroundings (putting lid on boiling pot)
Define (and give examples or compare where relevant) the following terminology: exothermic and endothermic
exothermic- heat exists or flows out of the system into surroundings endothermic- heat flows into the system from its surroundings
Define (and give examples or compare where relevant) the following terminology: extensive versus intensive properties
extensive properties- depend on the amount of sample (mass and volume) intensive properties- do not depend on the amount of sample being examined and are particularly useful in chemistry because many intensive properties can be used to identify substances (density and color).
what info is most important in determining the size of an orbital?
n-principal quantum number (energy level)
Define (and give examples or compare where relevant) the following terminology: open system
open system- matter and energy can be exchanged with surroundings (boiling pot of water on stove)
solute
other substance, one to be dissolved in the solvent
atomic orbital
region of probability where an e- can be found (s, p, d, and f orbitals)
Describe the shapes of orbitals for a given set of quantum numbers through n = 3
s- orbital= spherically symmetric p- orbital= peanut d-orbital= four petal flower f-orbital= 7 petal 3-d flower
Define (and give examples or compare where relevant) the following terminology: universe
universe- . All spacetime, matter, and energy, including the solar system, all stars and galaxies, and the contents of intergalactic space, regarded as a whole.
For a given chemical reaction, determine the enthalpy of reaction from standard enthalpies of formation
write equation you want as sum of mini questions. manipulate mini equations until desired one is achieved molecules have to be in the same state, multiply everything by the coefficient, don't forget to change the sign if equation is flipped
elemental composition of a substance
%mass composition of element= ((#of atoms)(atomic weight)/ formula weight of substance))100
Define and compare properties associated with classical particles and waves: speed
**all electromagnetic radiation moves at the same speed, namely, the speed of light**
what values are needed to determine the energy of an electron in a many-electron atom?
1. n (principal quantum number)---->>can have any positive integer value, (Bohr model), energy level of the e-, the larger n is the farther away from the nucleus it is. 2. l (angular momentum)---->>can have any value from 0 to (n-1), describes the shape of the orbital, l=0 (s orbitals; spherical), l=1 (p orbitals; lobes that extend outward, peanut shape) there are 3 per energy level l=2 (d orbitals) 5 per energy level l=3(f orbitals) 7 per energy level
Explain what aspects of the electron orbitals and other properties are governed by each of the four orbital quantum numbers n, l, ml, and ms , and be able to list the possible values for each
1. n (principal quantum number)---->>can have any positive integer value, (Bohr model), energy level of the e-, the larger n is the farther away from the nucleus it is. 2. l (angular momentum)---->>can have any value from 0 to (n-1), describes the shape of the orbital, l=0 (s orbitals; spherical), l=1 (p orbitals; lobes that extend outward, peanut shape) there are 3 per energy level l=2 (d orbitals) 5 per energy level l=3(f orbitals) 7 per energy level 3. m sub 1 (magnetic quantum number)--->>>any value from -l to l, including zero. -determines how many orbitals there are of a type per energy level -describes a specific orbital among a particular set 4. spin quantum number, m sub s---> only values are +1/2 or -1/2.
Heinsenberg's Priciple (uncertainty principle)
A principle stating there is an inherent uncertainty in the precision with which we can simultaneously specify the position and momentum of a particle. This uncertainty is significant only for particles of extremely small mass, such as electrons. ▲x= uncertainty in position ▲(mv)= uncertainty in momentum h= planck's constant *we essentially have no idea where the electron is located in the atom as the uncertainty in position of the electron is an order of magnitude greater than the size of the atom*
Pauli Exclusion Principle
An atomic orbital may describe at most two electrons, each with opposite spin direction
Aufbau Principle
An electron occupies the lowest-energy orbital that can receive it. -can use this to determine the e- configuration of any atom
bohr's model and its limitations
Bohr's model 1. only orbits of certain radii, corresponding to certain specific energies 2. an electron in a permitted orbit is in an "allowed" energy state. 3. energy is emitted or emitted or absorbed by the electron only as the electron from one allowed energy state to another. Limitations -explains ONLY the line spectrum of the hydrogen atom -avoided the problem of why the negatively charged electron would not just fall into the positively charged nucleus -electrons orbiting the nucleus at a fixed distance is not a realistic picture. Two things that are correct: **1. electrons exist only in certain discrete energy levels, which are described by quantum numbers. **2.energy is involved in the transition of an electron from one level to another.
Apply the definition of P-V work to calculate the work done for constant pressure and constant volume processes; explain the sign convention choice for P-V work
Ethalpy- (H) the internal energy plus the product of the pressure P, and volume V, of the system: H= E+PV (E, P, V, and H are all state functions) w=-P▲V (when pressure is constant in a process) gas expands- the system does work on the surroundings (negative w) gas is compressed- negative ▲v (volume decreases), w is therefore positive, meaning work is done on the system by the surroundings
Use the Pauli principle and Hund's rule to determine the number of unpaired electrons in an atom, and hence whether the atom is paramagnetic or diamagnetic; know the exceptions to the usual orbital diagrams that occur for Cr and Cu
Pauli exclusion principle- no two electrons in an atom can have same set of four quantum numbers. If we want to put more than one electron in an orbital we must assign different m values to the electron. Hund's rule- for degenerate orbitals, the lowest energy is attained when the number of electrons having the same spin is maximized. (based on the fact that electrons repel one another). parallel spins- single electrons in a given sub shell all have the same spin magnetic quantum number. paramagnetic- unpaired electrons diamagnetic- electrons all have paired spins ***Cr instead of [Ar] 4s^2 3d^4----> goes to 4s^1 3d^5 ***Cu instead of [Ar} 4s^2 3d^9--->goes to 4s^1 3d^10 ^^^These are due to the closeness of the 3d and 4s orbital energies. It frequently occurs when there are enough electrons to form precisely half-filled sets of degenerate orbitals (Cr) or a completely filled d subshell (Cu).
Define and compare properties associated with classical particles and waves: energy
Planck's Hypothesis of the Quantum Theory states that energy is emitted in quanta, little packets of energy, instead of a continuous emission. He stated that energy emitted is related to the frequency of the light emitted. Planck's hypothesis states that a quantum of energy was related to the frequency by his equation E=hν.
Discuss how these experiments led to the various hypotheses of Planck, Einstein, Bohr, and deBroglie regarding the wave nature of matter, and use the equations they proposed to carry out calculations relating energy to frequency, momentum to wavelength, and the energies of Bohr orbits in hydrogen-like atoms to line spectra and ionization energies
Planck- matter can emit and absorb energy only in whole numbers (E=hv). E=energy, h=planck's constant, v=frequency of the radiation Einstein- light is a stream of photons rather than a wave. (E=hv). E=energy, h=planck's constant, v=frequency of the light Bohr- explained how electrons could jump from one orbit to another only by emitting or absorbing energy in fixed quanta deBroglie- an electron moving about the nucleus of an atom behaves like a wave and therefore has a wavelength. wavelength= h/(mv) h- Planck's constant m-mass v-velocity mv- momentum
Discuss the physical interpretation and meaning of the solutions to the Schroedinger equation, in particular the wavefunction as a probability amplitude and the square of the wavefunction as a probability density
Schrodigner's wave equation- incorporate the wave-like and particle-like behaviors of the electron. wave function- A mathematical description of an allowed energy state (an orbital) for an electron in the quantum mechanical model of the atom; it is usually symbolized by the Greek letter psi (square of psi provides info about the electron's location when it is in a n allowed energy state). probability density (electron density)- A value that represents the probability that an electron will be found at a given point in space.
Describe in words and in equations the first law of thermodynamics, in the "system" points of view (focused on changes in internal energy of the system in relation to heat flow and work done on the system)
The internal energy of a system changes in magnitude as heat is added to or removed from the system or as work is done on or by the system. Changes in internal energy: ▲E= q +w q=heat added or liberated from the system w=work done on or by the system When heat is added to a system or work is done on a system, its internal energy increcses.
Define and compare properties associated with classical particles and waves: frequency
The number of times per second that one complete wavelength passes a given point. -expressed in cycles per second (hertz)
Define and compare properties associated with classical particles and waves: momentum
The relationship between momentum and wavelength for matter waves is given by p = h/λ the quantity (mv) for any object is momentum momentum The product of the mass, m, and velocity, v, of an object.
Define and compare properties associated with classical particles and waves: velocity
The velocity with which the wave travels in space is called the wave velocity. It is defined as 𝑣=𝑓𝑟𝑒𝑞𝑢𝑒𝑛𝑐𝑦∗𝑤𝑎𝑣𝑒𝑙𝑒𝑛𝑔𝑡ℎ. Particle velocity- is the velocity with which the particles are vibrating to transfer the energy in form of a wave. wave velocity- remains constant (provided the density of medium and frequency of source is constant), whereas particle velocity depends on the time (for a particular particle) or depends on where the particle is (for a particular time).
Explain what is meant by thermochemistry and how the first law of thermodynamics relates to chemical reactions
Thermochemistry- relationships between chemical reactions and energy changes that involve heat. First law of thermodynamics- energy is conserves, any energy that is lost by a system must be gained by the surroundings
Describe and compare constant volume calorimetry and constant pressure calorimetry, including the experimental setups, how the heat of reaction is determined in a calorimetric experiment, and how the measured heat in each experiment relates to delta E or delta H
constant volume calorimetry- 1.experimental setup: bomb chemistry 2. how heat is determined: The heat released when combustion occurs is absorbed by the water and the various components of the calorimeter (which all together make up the surroundings), causing the water temperature to rise. The change in water temperature caused by the reaction is measured very precisely. -----Because reactions in a bomb calorimeter are carried out at constant volume, the heat transferred corresponds to the change in internal energy, ∆E, rather than the change in enthalpy, ∆H. constant pressure calorimetry: 1. experimental setup-coffee cup 2. how heat is determined- measure the temperature change of the solution and assume that any changes are due to heat transferred from the reaction to the water (for an exothermic process) or transferred from the water to the reaction (endothermic). Delta E- Delta H- it is equal to the measured heat, change in temp, specific heat, and mass.
Describe how trends in n and Zeff across a period and down a group in the periodic table affect orbital size and stability
effective nuclear charge- The net positive charge experienced by an electron in a many-electron atom; this charge is not the full nuclear charge because there is some shielding of the nucleus by the other electrons in the atom. ^^^accounts for the combination of nuclear attraction and electron repulsion (Zeff<Z). Zeff= Z -S, where is S is the screening constant which is the amount of screening of the nuclear charge. *for valence e- the value of S is usually close to the number of core electrons in the atom.
ionization energy
electron being removed from an atom
Distinguish between energy levels and energy states or orbitals, and determine the number of degenerate orbitals
energy level (energy state)- fixed amount of energy (n=1,2,3..) orbital- An allowed energy state of an electron in the quantum mechanical model of the atom; the term orbital is also used to describe the spatial distribution of the electron. An orbital is defined by the values of three quantum numbers: n, l, and ml . degenerate orbitals- have the same energy (p orbital=3, d orbital =5, f orbital=7).
Describe in words and in equations the first law of thermodynamics, in the "global" (focused on changes in internal energy in the system, surroundings, and universe)
first law of thermodynamics- energy can be neither created not destroyed only transformed. internal energy- sum of all the kinetic and potential energies of the components of the system change in internal energy= delta final- delta initial positive deltaE-- system has gained energy from its surroundings negative deltaE-- system has lost energy to its surroundings. **any increase in the energy of the system is accompanied by a decrease in the energy of the surroundings and vice versa**
degenerate orbitals
have the same energy
Explain how the wave functions or atomic orbitals that result from solving the Schroedinger equation for hydrogen-like atoms relate to probability amplitudes, probability densities, and boundary surface plots for electrons
higher the amplitude- greater the probability of finding an electron there, probability density. boundary surface plots- represents the probability, psi^2. The origin of the coordinate system is at the nucleus.
electron affinity
how much energy is released when we add an electron to a species
DeBroglie hypothesis
if radiant energy could behave as though it were a stream of particles (photons), could matter also possibly show the properties of wave? Suggested: that an electron moving about the nucleus of an atom behaves like a wave and therefore has a wavelength.
Define and compare properties associated with classical particles and waves: intensity
intensity-number of photons per unit area of incidence per unit time, (since we consider energy is quantized).
relationship between kinetic and potential energy
inverse of each other. as d increases, potential energy gets smaller
Define (and give examples or compare where relevant) the following terminology: isolated system
isolated systems- neither energy nor matter can be exchanged with surroundings (thermos)
what info is needed to determine the general shape of an orbital?
l. the angular momentum quantum number, l, (also referred to as the secondary quantum number or azimuthal quantum number) describes the shape of the orbital that an electron occupies.
Describe the main experimental results that led to the quantum theory of light and matter, including the line emission spectra of atoms.
line spectrum- A spectrum that contains radiation at only certain specific wavelengths; it is unique to each element. Balmer's equation allows us to calculate the wavelength of all the spectral lines of hydrogen. Each colored line un such spectra represents light of one wavelength . **difference in energy levels is equal to the energy of the photon**
quantum numbers
location and energy of an e- in an atom
Define and compare properties associated with classical particles and waves, e.g. mass
mass is not an intrinsic property of the particle. Instead, mass is basically a measure of the particle energy
Define (and give examples or compare where relevant) the following terminology: processes and changes of state
matter changes from one state to another; They are reversible changes that do not change matter's chemical makeup or chemical properties.
what info is needed to determine the orientation of an orbital?
ml- The magnetic quantum number distinguishes the orbitals available within a subshell, and is used to calculate the azimuthal component of the orientation of orbital in space
Describe the main experimental results that led to the quantum theory of light and matter, including the photoelectric effect
photoelectric effect- the emission of electrons from a metal surface induced by light. light shining on a clean metal surface causes electrons to be emitted from the surface a minimum frequency of light, different for different metals, is required for the emission of electrons (if light has frequency less than the threshold no electrons are emitted) photon- smallest increment (a quantum) of radiant energy; a photon of light with frequency v has an energy equal to hv. E=hv (each photon must have an energy equal to the Planck constant times the frequency of the light) work function- certain amount of ENERGY that is required for the electrons to overcome the attractive forced holding them in the metal. **increasing the intensity of the light source doesn't lead to emission of electrons from the metal; only changing the frequency of the incoming light has that effect** intensity of light- number of photons striking the surface bu not the energy of each photon when the frequency is such that photons have energy greater than the work function of the particular meta, electrons are emitted; any excess energy of the photon is converted into kinetic energy of the emitted electron. ENERGY OF LIGHT DEPENDS ON ITS FREQUENCY. EINSTEIN'S THEORY OF LIGHT AS A STREAM OF PHOTONS RATHER THAN A WAVE.
Define the following atomic properties: and electron affinity; describe the periodic trends in each of these properties and how they relate to the underlying trends in n and Zeff; and finally, be able to rank a series of atoms according to the values of these properties
practice
Determine electron configurations and orbital diagrams for the ground electronic states of atoms in the periodic table through period 4 by applying the Aubau Principle along with the Pauli exclusion principle and Hund's rule, and relate these electron configurations to the position of an atom in the periodic table
practice e- configurations
effective nuclear charge
property of matter; how tightly an electron are held around an atom; relates to other periodic trends; increases from left to right; as the protons increase they are able to pull the e- in much tighter -each shell has a different effective nuclear charge
Describe the main experimental results that led to the quantum theory of light and matter, including the spectrum of blackbody radiation.
quantum theory: tells us that both light and matter consists of tiny particles which have wavelike properties associated with them. Light is composed of particles called photons, and matter is composed of particles called electrons, protons, neutrons. **blackbody radiation- the emission of light from hot objects, because the objects studied appear black before heating. Experiment: Plack's experiment- he proposed that energy can be either released or absorbed by atoms only in discrete "chunks" of some minimum size. Quantum- is the smallest quantity of energy that can be emitted or absorbed as electromagnetic radiation. E=hv (Energy, E, of a single quantum equals a constant times the frequency of the radiation) Planck's constant (h)- 6.626x10^-34 (J-s) **matter can emit and absorb energy only in whole number multiples of hv (hv, 2hv, 3hv), values are restricted to certain quantities***
Define the standard enthalpy of formation, the related standard states, and what this definition implies as the reference energy choice for elements
standard enthalpy of formation- ▲H(f)-- is the change in enthalpy for the reaction that forms one mole of the compound from its elements with all substances in their standard states. elements (in standard state)-->compound (1 mol in standard state) ▲H(rxn)=▲H(f) standard states- where element exists in standard conditions in its most stable form **more stable= lower-energy**
Define (and give examples or compare where relevant) the following terminology: state function and path dependence/independence
state functions: properties that are determined by the state of a system regardless fo how that condition was achieved (energy, pressure, volume, temperature) path function- does depend on the route that got the system to that point. path independent variables- state functions--- state the material started in and ended in. path dependent variables- heat and work-- amount of work or heat needed to make the change depends on HOW the process was performed, not just what state the material started in and ended in.
Define (and give examples or compare where relevant) the following terminology: state of equilibrium
state of equilibrium- state in which the rate of the forward reaction equals the rate of the backward reaction
solvent
substance present in the greatest quantity
Define (and give examples or compare where relevant) the following terminology: surroundings
surroundings- everything that lies outside the system we study
Define (and give examples or compare where relevant) the following terminology: system
system- portion we single out for study
slater's rule
the actual charge felt by an electron is equal to what you'd expect the charge to be from a certain number of protons, but minus a certain amount of charge from other electrons.
Define and compare properties associated with classical particles and waves: wavelength
the distance between identical points on successive waves -wavelength distribution of the radiation depends on temperature
enthalpy of reaction (heat of reaction)
the enthalpy change that accompanies a reaction
Use the relation between ▲E and ▲H to determine one from the other for chemical reactions involving gases
▲E AND ▲H both represent changes in molecular structure bc for most reactions, the work (w) component is very small due to small changes in volume. For reaction without gases, ▲V=0, so ▲H=▲E For reactions involving gases, w=-P▲V=-RT▲n, thus the value of work depends on whether there is a large difference in the number of moles of gases before and after a reaction. -If ▲n=0, ▲H=▲E -If ▲n<0, ▲H<▲E -If ▲n>0, ▲H>▲E
