ATOM

• Element in periodic table are arranged according to atomic number
• • Atomic number = number of protons in nucleus 
• • Electrons with the highest energy levels exist in the outermost shell. 
• • Electron in the valence shell called valence electrons.
• • The term valence is used to indicate the potential required to removed any one of these electrons. 
• Conductors

  • material that easily conducts electrical current.
• • The best conductors are single-element material (copper, silver, gold, aluminum)
• •  One valence electron very loosely bound to the atom
• Insulators

  • material does not conduct electric current
• • valence electron are tightly bound to the atom – less free electron
• Semiconductors

  •   material between conductors and insulators in its ability to conduct electric current
• • SEMICONDUCTOR in its pure (intrinsic) state is neither a good conductor nor a good insulator
• •  most commonly use semiconductor ; silicon(Si), germanium(Ge), and carbon(C).
• SEMICODUCTOR contains four valence electrons
• Doping -the process of creating N and P  type materials
• Two types of doping – trivalent (3 valence e-) & pentavalent (5 valence e-)
• p-type material – a semiconductor that has added trivalent impurities
• n-type material – a semiconductor that has added pentavalent impurities
• •  P-materials are doped with trivalent impurities
• • N-materials are doped with pentavalent impurities
• • P and N type materials are joined together to form a PN junction.
• • A diode is nothing more than a PN junction.
• • At the junction a depletion region is formed.
• Reporting Findings


  Ethical responsibility extends to reporting findings accurately and responsibly.