General Chemistry I - Ch.1-4 (Exam 1)

Protons

postively charged particles found in the nucleus

Neutrons

electronically neutral particels found in the nucleus

Electrons

negatively chraged particles distributed around the nuclues;
light, mass is negligible

Atomic Number (Z)

number of protons in the atom (determines the identity of the element) ; Atoms are neutral p⁺=e^-

Mass Number (A)

the total number of protons and neutrons

Isotopes

atoms that have the same atomic number (Z), but different mass numbers (A) ; AKA. a different number of neutrons; typically exhibit very similar chemical properties

Atomic Mass

the mass of an atom in atomic mass units (amu). ; the average mass of the isotopes for a given element

Average Atomic Mass

=(isotopic mass)(natural abundance) (for each isotope)

Molar Mass

the mass in grams of one mole of the substance

Grams —> Moles

divide by molar mass

Atoms —> Moles

divide by N_A (avagardo’s number)

Moles —> Grams

multiply by molar mass

Moles —> Atoms

multiply by N_A (avagardo’s number)

Energy (J)

the capacity to do work or transfer heat ; either kinetic or potential

Kinetic energy (E_k)

the energy of motion

Thermal Energy

the random motion of atoms and molecules ; can be determined by measuring temp. (slow motion, small amt of thermal energy —> dependant on mass and speed)

Cold V. Hot (Thermal Energy)

High temp= larger thermal energy ; Cold temp= small amt. of thermal energy

Absolute Zero (Thermal energy)

Theorhetically- nothing is moving (frozen) at 0 Kelvin @ a fixed postion

Potential Energy

energy possed by an object by virtue of it’s postion: two types: chemcial & electrostatic energy

Chemical Energy

energy stored within the structural units of chemical substances (energy between bonds)

Electrostatic Energy

the potential energy that results from the interaction of charged particles (ex. pos and neg charge) —> attraction force!

Law of Conservation of Energy

energy can neither be created nor destroyed; kinetic and potential energy are interconvertible BUT total energy of universe is a fixed value

Light (radiant energy)

produced by oscillating motion of electric charge; Electromagnetic (EM) radiation; light propagates through space

Wavelength

(λ) ; length of a cycle (nm)

Frequency

v ; the numebr of cycles per sec (HZ)

Amplitude

the vertical distance from the midline of a wae to the top of the peak or the bottom of the trough

Energy & Frequency

Direct Relationship (high frequency = high energy = short λ)

Energy & Wavelegth

Inverse Relationship (long λ = low energy = low frequency)

kilo (k)

10³

deci (d)

10^-1

centi ( c)

10^-2

milli (m)

10^-3

micro (µ)

10^-6

nano (n)

10^-9

pico (p)

10^-12

Solve for Wavelength

λ = c/v

EM Spectrum: Shortest λ? longest v?

CONTINUOUS: Gamma rays, X-rays, Ultraviolet, Visible (VBGYOR), Infared, Microwaves, Radiowaves

quanta

photons (in small packages/ budles); energy is quantized rather than continuous

Energy of a single quantum of energy is

E=hv

photoelectric effect

electrons are ejected from the surface of metal exposed to light of a min. v, called the threshold frequency. Number of e^- ejected is propotional to the intensity of the light

if E_photon = “binding energy” of e^- based on v

e^- ARE ejected

if E_photon > “binding energy” of e^- based on v

e^- ARE ejected & carry kinetic energy

if E_photon < “binding energy” of e^- based on v

e^- are NOT ejected

Gas Discharge Tube

electric discharge excites H atoms, transfers energy to e^-, as e^- relax, energy is emitted as light; NOT CONTINUOUS

Line spectrum = Atomic spectrum

specific to an element

Excitation

e^- moves to a higher energy level

Relaxation

e^- moves to a lower energy level

n=1

ground states, lowest energy, closest to the nucelus

Bohr’s Theroy of the Hydrogen Atom

electrons move around the nucleus in fixed orbits

when n > 1

excited state (less stable; further from nucleus), higher energy of the orbit

Energy difference between orbits formula

ΔE = -b ((1/n²_f) - (1/n²_i))

e- moves to a higher n orbit

less stable; e^- absorbs energy

e- moves to a lower n orbit

more stable, e^- releases energy as photons (light)

n_f > n_i

ΔE > 0, absorb energy

n_f < n_i

ΔE < 0, release energy

Heisenburg Uncertainty Principle

it is impossible to know both the momentum and postion of a partical with certainty —> Bohr’s model fail; e- cannot orbit the nucleus in a well-defined orbit

Schrodinger Equation and Quantum Mechanical Despcription of the H atom

gives shape and energy; when e- changes, e- changes to diff wave pattern, “atomic orbital”= e- position in the atom

e- density around nucleus

darker region, higher density, higher probablity of finding e-; each orbital has unique energy and e- density distribution

principal quantum number n

indicates orbital size; larger n, larger orbital; refers to the shell

angular moementum quantum number l

indicates orbital shape; l cannot equal n; s=0, p=1, d=2, f=3

magenetic quantum number m_l

indicates orbital orientation’ divides subshell into individual orbitals, intergers from -l to +l

Electron spin quantum number m_s

indicates direction of e- spin, -1/2 tor +1/2

Aufbau Principle

build up e- config. from lower energy orbitals

Pauli exclusion principle

maximus of 2 e- allowed in one orbital

Hund’s rule

Unpaired e- if an empty orbital is available

core electrons

inner electrons

valence electrons

outermost electrons; involved in bond formation; determine chemical properties; highest n indicates the valence e-

Group 1A

Alkali Metals

Group 2A

Alkaline Earth Metals

Group 6A

Chalcogens

Group 7A

Halogens

Group 8A

Noble Gases

Atomic radius

distance between nuclues of an atom and it’s valence shell

Metallic radius

half the distance between nuclei of two adjacent, identical metal atoms

Covalent radius

half the distance adjacent, identical nuclei in a molecule

ion

number of protons and electrons is no longer equal; atom is no longer neutral

ionization energy

energy required to remove an electron from an atom in the gas phase'; removing an e- results in a more pos. ion

cation

postive charge

anion

negative charge

adding/removing successive e-

becomes more difficult & takes more energy

Electron Affinity

Energy released when an electorn is added

x1,000,000

Mega (M)

x1000

kilo (k)

÷10

deci (d)

÷100

centi ( c)

÷1000

milli (m)