Atomic Theory, Nuclear Chemistry, and Radioactive Decay

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matter consists of very small, indivisible particles called atoms
JJ Thomson
Cathode ray expermient; discovered electrons
oil drop experiment; discovered exact chrage of an electron
law of conservation of mass
atoms cannot be created or destroyed in a chemical reaction
gold foil experiment; discovered nucleus has high mass and small volume (small, dense, and + charge)
+ charge; located in nucleus; Z; identifies the element
Atomic #
number of protons
neutral; located in the nucleus; A-Z
mass #
A; number of neutrons and protons
– charge; located outside the nucleus in orbitals; if atom is neutral, same as the # of protons
Avg Atomic Mass
weighted average of masses of naturally occuring isotopes; amu
atoms of the same element; same # of protons but different # of neutrons; different masses but same atomic number
general term for any isotope of the any element that is identified by # of protons and neutrons
isotope notation
A/Z X Ex: 3/1 H
hyphen notation
X-A Ex:Hydrogen-3
positively charged ions; # of p > # of e; have lost electrons; metals
negatively charged ions; # of p < # of e; gain electrons; nonmetals
mole concept
amount of a substance
Avogrados number
# of molecules in a mole; 6.02 x 10^23
molar mass
the mass of 1 mole of units of a substance
mass defect
the moving/leaving of mass in the form of energy in order to be stable
mass of an atom
avg mass of protons, meutrons, and electrons
strong nuclear force
gravity at the atomic value
when the identity of the element changes in a nulcear reaction
half life
amount of time it takes for half of a sample to decay into another
radioactive decay
emission of radiation; becoming more stable
alpha emission
weakest; restricted to heavy nuclei; above band of stability; 4/2 He
beta emission
mass doesnt change only atomic #; above band of stability; always on the product side; electron emitted; 0/-1 B
Positron Emission
decrease # of protons by converting into a neutron by emitting a positron; 0/+1 B; same mass as electron but + charge
Electron Capture
too many protons in nucleus; electrons captured by nucleus; always on reactant side; 0/-1 e
Gamma Emission
highest energy; has no charge, mass, protons, neutrons; never see these rays; most powerful; 0/0 y
Geiger Counter
detects radiation by counting electron pulses carried by gas ionized by radiation; radiation ionizes gas so elctric current can flow which makes beep
very heavy nucleus that seperates into more stable nuclei
light mass nuclei combine to form a heavier, more stable nucleus; stronger than fission; gives off more energy
Categories: Nuclear Chemistry