STRUCTURE OF THE ATOMREVIEW
NUCLEUS CONTAINS
ATOMIC NUMBER (Z) =
MASS NUMBER (A) =
ISOTOPES ARE
PROTONS AND NEUTRONS
# of PROTONS
PROTONS + NEUTRONS
SAME ELEMENT WITH DIFFERENT NUMBER OF NEUTRONS
Lithium - 6
ISOTOPE SYMBOL and ISOTOPE NAMEElement Name
Element SymbolMass Number
Atomic Number
Chemical Reactions
Nuclear ReactionsIsotopes of one element are converted to isotopes of another element, and hence the chemical identity of individual atoms changes. The nucleus is involved rather than outer electrons and the release of energy is large and defined by E = mc2
Atoms are rearranged to form new substances while keeping the chemical identity of the individual atoms. Only outer electrons are involved and the
release of energy is small.
VS.
RADIOACTIVITYthe spontaneous breaking apart of unstable nuclei in
which small particles of matter and/or electromagnetic radiation are emitted
Credited with discovering radioactivityA)Studied uranium compounds and their ability to fluoresce or give off visible light after being exposed to sunlight
B)Discovered that uranium gives off invisible rays at all times
C)The rays penetrate the light proof cover of photographic film and expose it
Henri Becquerel
A) Studied uranium and its oresB) Discovered uranium and uranium compounds are only mildly radioactiveC) Pitchblende (a uranium ore) has four times the amount of radioactivity expected based on its uranium content due to other isotopes (Ra and Po) present as a result of U natural radioactive decayD) Radium is more than a million times as radioactive as uranium and polonium is more than 5000 times as radioactive as radium
Marie and Pierre CurieCredited with discovery of Ra and Po
Properties of Radioactive Nuclides:
1) They affect the light-sensitive emulsion on a photographic film
2) Produce an electric charge in the surrounding air
3) They produce fluorescence / phosphorescence with certain compounds
4) Their radiations have physiological effects minimized by time, distance, and shielding
5) They undergo radioactive decay (emit nuclear or ionizing radiation)
Nuclear Radiation the particles and energy produced when a nucleus
undergoes radioactive decay
1)Natural radioactive decay: an unstable element decays to form a more stable nucleus
2)Artificial: man-made transmutations done in linear accelerator or nuclear reactors
Transmutation
changing the nucleus of one isotope into a different isotope or element
Nuclear Stability
Affected by the ratio of neutrons to protons
Isotopes with an atomic number 1-20 have a neutron to proton ratio of 1:1
Isotopes with an atomic number between 20-83 have a neutron to proton ratio of 1:5
All nuclei above atomic number 83 are unstable and are always radioactive
Nuclear Decay TypesBeta Decay
A high-energy, fast-moving electron is ejected from the nucleus, effectively changing a neutron into a proton
Charge:Mass Number: Identity Change:
Electron Capture
A 1s electron is captured by the nucleus, effectively changing a proton to a neutron
Charge:Mass Number: Identity Change:
Alpha Decay A high-energy, fast-moving +2 charged helium ion is ejected from the nucleus 1) Pose the greatest health risk
Charge:Mass Number: Identity Change:
Gamma-ray Emission
Gamma radiation accompanies other types of radioactive decay
Charge:Mass Number: Identity Change:
Neutron Decay or Capture
Neutrons can be emitted or captured by isotopes to increase their stability 1) they pose the next greatest health hazard after alpha particles
Example of Neutron Capture
Example of Neutron Emission
Charge:Mass Number: Identity Change:
Decay Properties
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