structure of the atom review

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