CHEM 1161 Exam 1

What is the name and symbolism that corresponds to the property distance in relation to common SI units?

meter, m

What is the name and symbolism that corresponds to the property mass in relation to common SI units?

gram, g

What is the name and symbolism that corresponds to the property volume in relation to common SI units?

liter, L

What is the name and symbolism that corresponds to the property time in relation to common SI units?

second, s

What is the name and symbolism that corresponds to the property temperature in relation to common SI units?

kelvin, K

What is the name and symbolism that corresponds to the property amount of substance in relation to common SI units?

mole, mol

What are the names, symbols, and factors of the SI unit prefixes of importance?

-mega, M, 10^6

-kilo, k, 10^3

-deci, d, 10^-1

-centi, c, 10^-2

-milli, m, 10^-3

-micro, symbol mu, 10^-6

-nano, n, 10^-9

-pico, p, 10^-12

orbitals

the spatial locations of electrons in the electron cloud

electromagnetic radiation

the vast spectrum of radiation that encompasses visible light

electromagnetic spectrum

encompasses all types of electromagnetic radiation

visible light

-portion of electromagnetic spectrum visible to humans

-has a wavelength between 400 and 700 nm

What are the main properties of waves?

wavelength, frequency, amplitude, velocity

wavelength

distance between two identical points in a wave

frequency

number of wave cycles (wavelengths) that pass a given point per unit time (usually 1 s)

What is the type of relationship that wavelength and frequency have?

inverse relationship

What is the relationship between wavelength, frequency, and energy of light?

short wavelength = high frequency = high energy

long wavelength = low frequency = low energy

amplitude

one-half the height between a crest and a valley of a wave

velocity

the speed at which the wave is traveling

What is the equation for calculating the speed of a wave?

wavelength * frequency

speed of light [in a vacuum]

2.998 x 10^8 m/s

What does the speed of light represent relative to electromagnetic radiation?

value at which all forms of electromagnetic radiation move

hertz (Hz)

-frequency unit of inverse second (s^-1)

-1 of these = 1 cycle/wavelength per second

-sometimes represented as megahertz (MHz); in these instances, make sure to convert

refraction

-the bending of a wave when it passes from one medium to another (demonstrates the wave behavior of light)

-i.e. white light passing through air and hits a prism; light bends when it hits the prism; different wavelengths contribute to different angles at which light bends)

photoelectric effect

-light strikes a metal surface

-electrons are ejected from the metal atoms to the positive pole and create a current, but only if the light/radiation is of sufficient energy

-originally thought that the amplitude of the light wave (brightness) determines its energy; later observed that it's actually the frequency (threshold frequency) of the light

photons

light particles

Planck's constant

6.626 x 10^-34 J*s

What is the equation for solving for the energy of a photon?

Planck's constant frequency (Planck's constant speed of light / wavelength)

wave-particle duality

quality of light whereby light is best described as a wave in some situations and as a particle in others

Fraunhofer lines

series of narrow dark lines existent in the spectrum of sunlight that proves sunlight is not continuous

What can elements do with light?

emit (release) light and absorb light

line spectrum

emission spectra consisting of discrete, narrow, bright lines and mostly darkness that are produced by elements (few bright lines explained by fact that elements release only certain wavelengths of light)

absorption spectrum

-produced by the light which is not absorbed by a gaseous element when white light is shone at the element (the light passes through a prism to produce this)

-each element takes in its own wavelengths in addition to emitting them

What is the relationship between electrons and absorption spectrum?

the more electrons an element has, the more complicated the absorption spectrum is

***more electrons = more energy states = more ways of rising in energy level = more wavelengths of light that can be absorbed via the excitement of electrons

What is the relationship between wavelengths emitted versus absorbed by an atom?

wavelengths emitted by an atom = wavelengths absorbed by the atom

***change in energy from a lower energy state to a higher one = change in energy from a higher energy state to a lower one

***in the equation E = hc/lambda, h and c are constants so they don't change, and the absolute values of the changes in energy from a lower energy state to a higher one and vice versa are the same, so the wavelength/lambda produced in the calculation is the same for emission and absorption

Why does the Sun's emission spectrum have Fraunhofer lines?

the Sun releases all wavelengths of visible light, but gaseous atoms in the outer regions of the Sun absorb characteristic wavelengths of light passing through them on its way to Earth

What happens when an atom emits light?

it emits energy and moves from a high energy state to a low energy state

What happens when an atom absorbs light?

it absorbs energy and moves from a low energy state to a high energy state

What are absorption and emission line spectra evidence of?

an atom can only exist in discrete energy states

***discrete energy states = certain absorptions and emissions of energy = certain photons of light produced = certain wavelengths produced

quantized

a property with only certain allowed (discrete) values

***describes the energy of an atom

Bohr model

-proposed that an electron travels around the nucleus in a circular orbit

-these orbits are stable and have quantized energy

-the further the orbit from the nucleus, the higher its energy

>the higher the energy of the orbit, the more unstable the orbit is

-when an atom absorbs or emits light, the electron travels between orbits

limitations of the Bohr model

-does not work for atoms with two or more electrons

-didn't account for interactions between electrons of atoms with two or more electrons

quantum theory

if light can be treated as a particle, then a particle, such as an electron, can be treated as a wave

de Broglie equation

-lambda = wavelength of the particle

-h = Planck's constant = 6.626 x 10^-34 J*s

-m = mass of the particle

-v = speed of the particle

***used to calculate the wavelength of any particle in motion

Why don't we notice wavelike properties with macroscopic particles?

macroscopic particles have a large mass -> wavelength is very small, according to de Broglie's equation

***the behavior of large particles can be described as particles, not waves

How can objects be located and their speed be measured?

by reflecting electromagnetic radiation off the object

***the electromagnetic radiation must have a wavelength comparable in length to the size of the object

***for electrons, the only radiation with a wavelength this short is gamma radiation

What is the problem with using gamma rays for a measurement like this?

gamma rays are very high energy and will knock the electron off course

Heisenberg Uncertainty Principle

it is fundamentally impossible to determine simultaneously and exactly both the position and the momentum of a particle

What did Erwin Schrodinger say about finding electrons?

We can only specify the probability of finding an electron in a particular region of space known as an orbital

What are the four quantum numbers?

***n, ℓ, mℓ describe the orbital that the electron likely occupies

***ms is associated with a property of the electron, not its orbital

Principal Quantum Number, n

-defines the distance of the orbital from the nucleus (increase in n = increase in distance from the nucleus)

-also called the shell number

-starting with n = 2, there are multiple orbitals that have the same distance from the nucleus / the same shell

Angular Momentum Quantum Number, ℓ

-defines the shape of an orbital

-allowed values: ℓ = 0 ,1, 2 ... (n-1)

-for ℓ = 0: s orbital

-for ℓ = 1: p orbital

-for ℓ = 2: d orbital

-for ℓ = 3: f orbital

-increase in ℓ = increase in complexity of the shape

shape of s orbital

sphere

shape of p orbitals

dumbbell / figure 8 shape

What happens when the shell of an orbital (n) increases?

-the size of the orbital increases

-energy generally increases

-the probability of the electron being farther from the nucleus increases

What happens when the angular momentum quantum number (ℓ) increases?

-the probability of the electron being farther from the nucleus also increases

-the energy of the orbital increases

-the complexity of the shape of the orbital increases

degenerate orbitals

-orbitals that have the same values of n and ℓ

-orbitals that have the same energy

-orbitals that belong to the same subshell

Magnetic Quantum Number, mℓ

-defines the orientation of an orbital in space around the nucleus of an atom

-value depends on ℓ (mℓ = -ℓ ... -1, 0, +1, ... +ℓ)

What equation can indicate the number of orbitals in the same subshell?

2ℓ + 1

How many allowed s orbitals are there?

one

How any allowed p orbitals are there?

three

How many allowed d orbitals are there?

five

Spin Quantum Number, ms

-associated with a property of the electron, not the orbital the electron is within

-either + 1/2 or -1/2

Pauli Exclusion Principle

-no electrons in an atom can have the same set of all four quantum numbers

-if any electrons in an atom occupy the same orbital, they have the same n, ℓ, and mℓ quantum numbers (they must have different ms values)

-two allowed ms values -> max of two electrons may occupy the same orbital -> one electron has ms = + 1/2 and the other has ms = - 1/2

electron configuration

-the distribution of electrons among the orbitals of an atom or ion

-coefficient represents n

-letter represents ℓ

-superscript is the number of electrons

ground state

most stable, lowest- energy state of a particle

***an atom is in this when electrons occupy orbitals of the lowest available energy

excited state

any state above the ground state

***an atom is in this when one or more electrons occupy orbitals that are not the ones of lowest available energy

Aufbau Principle

orbitals fill with electrons in order of increasing energy

notes on the periodic table/electron configuration

1. for s and p orbitals, the value of n is equal to the period (row) number

2. Elements in Groups 1 and 2 & Helium - Electrons are added last to an s orbital

3. Elements in Groups 13-18 except Helium - Electrons are added last to a p orbital

4. Transition metal elements - Electrons are added last to a d orbital, with "n" value that is one less, than the period number

5. Lanthanides and Actinides - Electrons are added last to an f orbital with "n" value that is two less than the period number

What are the s and p block elements called?

main-group/representative elements

orbital diagram

-representation of the electron configuration, showing the individual orbitals and the pairing arrangement of electrons

>parentheses, boxes, or lines represent individual orbitals

>single-headed arrows, up and down, indicate electrons

>follow the Pauli Exclusion Principle (max 2 electrons per orbital, electrons must have opposite signs)

Hund's Rule

-the lowest-energy electron configuration for degenerate orbitals is that with the maximum number of unpaired electrons

>this is because electrons are negatively charged and prefer maximum space between each other [to avoid repulsion]

-the unpaired electrons will have the same spin

-only after all degenerate orbital are half-filled will electrons begin to pair with opposite spins

condensed/noble gas electron configurations

electron configurations whereby electrons corresponding to the preceding noble gas are represented by the noble gas in brackets, and only electrons after the noble gas are explicitly shown

valence electrons

-the outermost electrons which lie farthest from the nucleus

>these electrons are in the shell of highest n value

>these electrons are the ones that normally participate in chemical reactions

>these electrons are of highest energy and of least stabilization by the nucleus

core electrons

-inner electrons which lie closer to the nucleus

>these electrons typically do not participate in chemical reactions

electron configuration of ions

-main group elements (s and p block) tend to form ions that have the same electron configuration as (are isoelectronic with) a nearby noble gas

>the stability of the noble gases is a result of their electron configurations (involve filled outer s and p orbitals, or frontier orbitals)

isoelectronic

species with the same electron configuration

cations

positive ions that form by the loss of electrons

anions

negative ions that form by the gain of electrons

electron configurations for main group cations

the electrons that are added last are removed first

>metals tend to form cations

electron configurations for anions

electrons are added to the orbital(s) of lowest available energy

>non-metals tend to form anions

properties of metals

-malleable

-ductile

-good conductors of heat & electricity

-consist of cations

-solid at room temp (except Hg)

properties of nonmetals

-brittle

-not good conductors of heat & electricity

-consist of anions

properties of metalloids

properties are intermediate of both metals and nonmetals

What are the different metalloids?

-Boron (B)

-Silicon (Si)

-Germanium (Ge)

-Arsenic (As)

-Antimony (Sb)

-Tellurium (Te)

-Astatine (At)

electron configurations for transition metal cations

-transition metals typically do not form ions that are isoelectronic with a noble gas

-electrons are lost first from an s orbital before a d orbital

What are the three main periodic properties?

1) Sizes of atoms and ions

2) Ionization energy

3) Electron affinity

atomic radius

-determined by measuring the distance between the nuclei of bonded atoms

What are the trends for atomic radii in the periodic table?

-radii increase down a group

>the valence electrons are in a shell of higher "n" value

>the valence electrons have a greater probability of being farther away from the nucleus

-radii decrease left to right across a period

>the number of protons increases, but the number of core electrons remains constant -> the amount of shielding remains almost constant -> the effective nuclear charge increases, and the radius gets smaller

effective nuclear charge (Zeff)

-the attraction toward the nucleus experienced by an electron

>for multi-electron atoms, Zeff < Z (# protons) due to shielding

-as this increases, the outermost electrons are pulled in more tightly, and the atomic radius decreases

What are the trends in ionic radii?

-cations are smaller than their parent atom

>less electrons -> less shielding, higher Zeff, smaller radii

>for main-group elements, all of the outermost (valence) electrons are lost when forming a cation

-anions are larger than their parent atom

>gain of electron(s) results in increased electron-electron repulsions

>more electrons -> more shielding, smaller Zeff, larger radii

ionization energy

-first ionization energy (IE1): the amount of energy required to remove the most loosely bound electron from a gaseous atom

-second ionization energy (IE2): the energy required tp remove the second most loosely bound electron

-is always a positive value (energy must be inputted to remove an electron)

-if this term is seen, assume IE1

What are the trends in first ionization energy (IE1)?

-in general, it increases across a period from left to right

>associated with an increase in Zeff

-in general, it decreases down a group from top to bottom

>associated with an increase in atomic radii

successive IE values

-they always increase

>result of greater electrostatic attraction between the electron and positive cation

>there is a large jump in ionization energy for the removal of the first core electron (core electrons are more strongly attracted to the nucleus)

electron affinity

-the change in energy for the process of adding an electron to a gaseous atom to form an anion

-this quantity is mostly negative

>this tells us that energy is lost

>the electron has an attraction for the nucleus of the atom

>the ion is usually more stable than the separated atom and electron

electron affinity values

-most negative values are within the halogens

>they can add one electron and become stable, given that they have a high Zeff)

-positive for noble gases because they don't need to accept electrons

>they already have full octets

What are the trends in electron affinity?

-in general:

EA becomes more negative from left to right across a period

>normally, easier to add an electron as the Zeff increases

>>there are some exceptions (i.e. noble gases)

Compound

-A substance made up of atoms of two or more elements joined together by chemical bonds

-The atoms combine in fixed whole number ratios

-the atoms combine to form either extended lattices or discrete particles called molecules

What are the two main types of compounds?

(1) covalent/molecular compounds

(2) ionic compounds

covalent/molecular compounds

compounds held together by covalent bonds

ionic compounds

compounds held together by ionic bonds