Democritus (discovery)
matter made of ‘atomas’; not divisible
John Dalton (discovery)
Dalton's theory
Dalton's theory
correct: all matter is composed of tiny particles called atoms, atoms combine in simple whole ratios to form compounds, atoms of 1 element cannot be changed into a new element during chemical reactions incorrect: all atoms of an element are identical (bc isotopes), atoms cannot be created, divided, or destroyed (atomic bombs)
JJ Thomson (experiment)
cathode ray experiment
JJ Thomson (discovery)
discovered electron; plum pudding model
Millikan (experiment)
passed oil drops through a pin hole into the middle of the charged plate and noticed drops suspending between the plates
Millikan (discovery)
determined velocity + mass of an electron; 9.11 x 10⁻³¹ kg; electron charge = negative
Ernest Rutherford (experiment)
gold foil experiment
Ernest Rutherford (discovery)
discovered proton; atom mostly empty space; electrons (in empty-ish space) surround proton + neutron (in dense) nucleus; transmutation (i think?)
James Chadwick (discovery)
discovered neutron; w/ mass nearly equal to proton; w/ no charge (neutral)
Niels Bohr (discovery)
discovered electron orbits; 7 circular orbits around nucleus (energy levels)
electron (discoverer/location/charge/symbol)
discoverer: thomson; location: outside nucleus; charge: negative (-); symbol: e⁻; most of atom volume; discovered first
proton (discoverer/location/charge/symbol)
discoverer: rutherford; location: inside nucleus; charge: positive (+); symbol: p⁺; discovered second
neutron (discoverer/location/charge/symbol)
discoverer: chadwick; location: inside nucleus; charge: neutral (0); symbol: n⁰; discovered third
nucleus
dense; protons + neutrons; very dense; small % of total volume
A.P.E.
atomic number = # of protons = # of electrons
M.A.N.
mass = atomic number + # of neutrons
atomic number
isotopes
atoms of same element, w/ dif. # of neutrons; identified by mass #
isotope (similarities)
chemically + physically; # of protons and electrons
isotope (differences)
atomic mass
weighted average of mass of isotopes of that element; expressed in amu (atomic mass number); usually not a whole number
atomic mass (equation)
(mass₁ * (abundance%₁) + (mass₂ * (abundance%₂); add on as many examples provided
nuclear chemistry
study of structure of atomic nuclei and the changes they undergo
nuclear reactions (vs. chem rx)
emit particles +/ rays; atoms converted to dif. element; involve p⁺, n⁰, and e⁻; large energy charges; rx rate not affected by temp, particle size, concentration, +/ catalysts
radioisotopes
isotopes w/ unstable nuclei (too few/many neutrons)
radioactive decay
unstable nuclei losing energy; emit radiation to become stable; spontaneous process; element redefined by new atomic #; types: alpha, beta, and gamma
alpha (α) (radiation)
emission of alpha particle; ⁴₂HE; positive; 4amu; shield: paper/air
beta (β) (radiation)
emission of beta particle (fast moving electron); ⁰-₁e / ⁰-₁β; negative; 1/1837amu (a.k.a. 0amu); shield: foil
gamma (ɣ) (radiation)
high energy electromagnetic radiation; ⁰₀ɣ; neutral; 0amu; shield: concrete
approx. energy (radiation)
high - gamma; medium - beta; low - alpha
penetrating power (radiation)
high - gamma; medium - beta; low - alpha
nuclear stability
when nucleus will not randomly decay
very stable elements
atomic # 1-20; 1:1 proton:neutron ratio
moderately stable elements
atomic # 21-82; 1:1.5 proton:neutron ratio
unstable/radioactive elements
atomic # 82+
transmutation
conversion of an atom of one element into an atom of another element; based on atom’s new atomic # after nuclear rx; discovered by Ernest Rutherford (i think?)
half-life
time it takes for half of a radioisotope’s nuclei to decay into its products; table format: # of half-lives | time | amount/mass
half-life (equation)
mₜ = m₀ * 0.5ⁿ; mₜ = amount/mass remaining, m₀ = initial amount/mass; n = # of half-lives (a.k.a. (= (total time) / (length of 1 half-life)))
nuclear reactions (types)
radioactive decay; nuclear disintegration; fission; fusion
nuclear disintegration
emission of a proton or neutron
fission
splitting of a nucleus (heavy nucleus into 2 approx. = parts); chain rx; can be slowed if controlled by neutron moderator (^ rx rate, ▼ speed) and neutron absorption (control rods to ▼ slow neutrons); not controlled → atomic bomb
fusion
combining of two nuclei (two light nuclei into one heavy); not occur under standard conditions
fusion (advantages)
inexpensive; no radioactive waste
fusion (disadvantages)
requires large amt of energy to start; hard to control
film badge
detects radioactive exposure; for small areas + amts
geiger counter
detects radiation amounts; for large amounts
radiation (uses)
radioactive dating; diagnose diseases; cancer treatment; x-rays; tumor treatment; study chem. rx; food irradiation; power plants; everyday items (ex: lanterns, heart pacemakers, and smoke detectors)