Chem 101 Unit One

Physical vs Chemical Properties

- Physical: don't change a substance's chemical makeup

- Chemical: change a substance's chemical makeup

Extensive vs. Intensive Property

- Extensive: depends on quantity of substance present (ex: mass)

- Intensive: doesn't depend on quantity of substance present (ex: color, melting point)

**"Intensive = Independent"

Law of Conservation of Energy

states that energy cannot be created or destroyed, but can change from one form to another

Kinetic vs. Potential Energy

- Kinetic Energy: energy of motion

- Potential Energy: energy by position/composition (stored energy)

Energy is ______________ when bonds are formed and ____________ when bonds are broken

released, absorbed

Sublimination

solid to gas

Deposition

gas to solid

Accuracy vs. Precision

- Accuracy: how close a result is to the true value

- Precision: how repeatable the result is

Temperature

measure of the average kinetic energy of particles

Kelvin to Celsius

K = C + 273.15

Changing the temperature of something by 1 degree Celsius (is/is not) the same as changing it by one Kelvin

is (even though they're different temperature systems, a change in one produces the same change in the other; their numerical values will just be different)

More decimal places in a number means (more/less) uncertainty

less

When adding/subtracting, the final answer should have...

the same number of decimal places as the number with the LEAST number of decimal places

ex: 2.6 + 10.517 = 13.1 (one decimal place)

When multiplying/dividing, the final answer should have...

the same number of sigfigs as the number with the LEAST number of sigfigs

ex: 2.6 * 10.517 = 27 (two sigfigs)

When solving a problem and trying to account for sigfigs, know that _______ values and _________ _________ between ___________ ____________ do NOT count

exact values (have infinite sigfigs), conversion factors, metric prefixes

When solving a problem, keep track of sigfigs after every...

mathematical operation

Diatomic Molecules

pure elements that exist as molecules (see image)

Cations vs. Anions

- cations = (+)

- anions = (-)

**cathode and anode are flipped

Protons vs. Neutrons vs. Electrons

- Protons: positive, in nucleus, weighs ~1.007 amu

- Neutrons: neutral, in nucleus, weight ~1.009 amu

- Electrons: negative, in electron cloud, weighs ~0 amu

Nuclide

fancy term for isotope

Thomson's Cathode Ray Tube Experiment

discovered the electron + its charge

Millikan's Oil Drop Experiment

discovered mass of electron

Rutherford's Gold Experiment (describe the original hypothesis, what happened during the experiment, and what they concluded from it)

- bombarded gold sheet with alpha (a) particles, which were positively charged

- thought that all a particles would go through b/c they assumed the "plum-pudding" model was correct (thought atom was a sphere of weak positive matter with electrons embedded throughout)

- some of the particles were deflected at large angles, indicating a region of dense positive charge (led to discovery of nucleus + nuclear view of atom)

When ionizing an element (changing its charge), you are changing its number of ________________.

electrons

Average Atomic Mass

weighted average of the masses of all of an element's existing isotopes

Isotope Symbol (format)

- mass number = number of protons + neutrons

- atomic number = number of protons

Metals (describe their properties)

- shiny and solid

- conductors of heat + electricity

- malleable (able to be hammered)

- ductile (able to be drawn out into thin wires)

**Mercury is an exception (is liquid)

Nonmetals (describe their properties)

- solids (brittle), liquids, and gases

- non-conductors

Metalloids (describe their properties

- shiny (like metals) but brittle (like nonmetals)

- semi-conductors

Mole

contains 6.022 10^23 (Avogadro's Constant*) atoms of a substance

Molecular Mass (what is it and what types of compounds DON'T have this?)

- sum of the masses of all of the atoms in a molecule (unit: u/molecule)

- ionic compounds DON'T have molecular mass b/c they're not made of molecules; instead have formula mass instead

Molar Mass (what is it and how does it compare to atomic/molecular mass?)

- mass (in grams) of one mole of an element

- it has the same NUMERICAL value as the atomic/molecular mass, but its unit is g/mol

Mass Spectrum Graph

- showcases relative abundance of each isotope

- x-axis is usually m/z (with z being one) or just mass (in u)

Wavelength (λ)

distance from one crest to the next

Frequency (describe its unit)

- the number of wavelengths that pass a fixed point each second

- unit = Hz (or s^-1 or 1/s)

What is the formula relating speed of light, frequency, and wavelength?

v = c/λ (any other variations of this also work!)

- v = frequency (in hz)

- c = speed of light (2.998 * 10^8 m/s)

- λ = wavelength (in meters)

Energy of a Photon (describe its equation(s), what each symbol represents, and the units that the energy is measured in)

E = hv OR E = h(c/λ)

- h = planck's constant (6.626 10^-34 Js)

- c = speed of light (2.998 * 10^8 m/s)

- v = frequency (in hz)

- λ = wavelength (in meters)

- E = energy in J/photon

How are wavelength, frequency, and the energy of a photon related?

- Frequency and energy are directly proportional

- Frequency and wavelength are inversely proportional

- Energy and wavelength are inversely proportional

ex: as wavelength increases, frequency and energy decrease

ex: as wavelength decreases, frequency and energy increase

Work Function

represents the minimum amount of energy needed to dislodge an electron from the surface of a material

What happens when excess energy (energy greater than the work function) hits the surface of a material?

the excess energy provides the electron being dislodged with more kinetic energy

Photoelectric Effect (what do we call the electrons that are involved in this effect?)

- occurs when metals/semi-conducters are illuminated and electrons are emitted

- these electrons are referred to as photoelectrons

Bohr Model (how does it work + what type of atoms does it apply to?)

- planetary model that displays various energy levels that electron can be at

- only applies to hydrogen-like atoms (atoms with one electron)

In Bohr's Model, electrons ________ energy when traveling to higher levels and ________ energy (which releases _____________) when going back to their ground state

absorb, emit, photons

Ground State vs. Excited State

- ground state = lowest energy, closest to the nucleus

- excited state = higher energy, when electron is farther from nucleus (n =/= 1)

Matter Waves (describe equation)

waves associated with moving particles

- λ = wavelength (in meters)

- h = planck's constant (6.626 10^-34 Js)

- m = mass (kg)

- v = speed/velocity

**mv = momentum

As the mass or speed of an object (its momentum) increases, its wavelength...

decreases

Standing Wave (what is it + how is it important in the structure of an atom?)

- wave that oscillates back and forth within a fixed space

- keeps electrons from being pulled into the nucleus

In Bohr's Model, each orbit has a specific _________ wavelength

integer

Heinsberg Uncertainty Principle

states that it is impossible to know both the position and velocity of an electron simultaneously

Orbital (what is it + how are they identified)

- region of space where the probability of finding an atom is high (represents the wave function squared, or Ψ^2)

- identified by a combination of three quantum numbers (n, l, ml)

Describe the meanings behind n, l, ml, and ms

- n = principal quantum number; indicates size + energy

- l = angular momentum number; defines orbital shape

- ml = magnetic quantum number; defines orientation

- ms = spin number; defines spin of electron

What values can n, l, ml, and ms have?

- n >= 1

- l: 0 to (n-1)

- ml: -l to l

- ms: +1/2 or -1/2

Define the values of l and the shapes they correspond to

l = 0 --> s (sphere)

l = 1 --> p (dumbbell)

l = 2 --> d (four-leaf clover OR dumbbell w/ doughnut shape in middle)

l = 3 --> f (complex)

Pauli Exclusion Principle (what is it and what did it help us realize?)

- states that no two electrons in the same atom can have the same set of quantum numbers

- proves that each orbital can only hold up to 2 electrons (one spin up, one spin down)

Isoelectronic

same electron configuration

In electron configuration, anything in the outermost shell (highest n-value) represents the electrons in the _____________ ____________

valence shell

**in the image, the orbitals in black represent the valence shell

If the n and l values of two electrons are the same, that means they are in the same _________________ and are in _______________ orbitals (orbitals that have the same energy)

subshell, degenerate

The closer an orbital is the nucleus, the ___________ its energy is

lower

Aufbau Principle

the lower-energy orbitals are filled first

Hund's Rule

one electron must be in each degenerate orbital before they are paired up

Radial Nodes vs. Planar Nodes (define what a node is + the different between these two types of nodes)

- Node: where there is zero electron density/areas where there is no probability of finding an electron

- Radial Nodes: spherical surface area where no electrons will be found (more common in the space between s orbitals)

- Planar Nodes: planes between orbitals where electrons will not be found (more common in space between p orbitals)