(L3) ATOMIC MODEL AND SUBATOMIC PARTICLES

• There are building blocks of matter that make up everything that exists in our world = ATOMS
• Atom


  Tiny, indivisible particles that make up all matter
• John Dalton


  • English chemist, physicist and meteorologist
  • Best known for introducing the atomic theory into chemistry
  • Researched color blindness (Daltonism)
• Dalton's Atomic Theory


  1. All elements are composed of tiny indivisible particles called atoms

  2. Atoms of the same element are identical. Atoms of any one element are different from those of any other element.

  3. Atoms of different elements combine in simple whole-number ratios to form chemical compounds

  4. In chemical reactions, atoms are combined, separated, or rearranged – but never changed into atoms of another element.
• Dalton was wrong about all elements of the same type being identical
• Atoms of the same element can have different numbers of neutrons, thus different mass numbers. These are called isotopes.
• Sir Joseph John Thomson

  • British physicist
  • Discovered the electron
  • Characterized the electron as a negatively charged particle
• Ernest Rutherford

  
  

  • New Zealander
  • Designed experiment to study alpha particle interaction with gold foil
  • Identified positively charged protons in the nucleus

  
• Niels Henrik David Bohr

  • Danish physicist
  • Made foundational contributions to understanding atomic structure and quantum theory
  • Visualized electrons rotating in orbits around the nucleus

  
• Electron


  • Negatively charged particle
  • Mass of 9.110 x 10^-28 g
  • Diameter believed to be less than 10^-12 cm
  • discovered by John Joseph Thomson
• Proton


  • Positive charge
  • Discovered by Eugen Goldstein
  • Number of protons represents the atomic number

  
• Neutron


  • Uncharged particle
  • Discovered by James Chadwick
  • Mass slightly greater than a proton
• Electrons can be shared or transferred among atoms
• For a given element, the mass number is the number of protons and neutrons (nucleons) in the nucleus
• Atomic Number


  Unique, distinctive number of protons of an element
• Mass Number


  Sum of the numbers of protons and neutrons in an atom
• Cells


  tiny building blocks in the body, but are not the tiniest particles in the world
• Thomson's Model (Plum-Pudding/Raisin-Bread Model)


  • solid mass of positive charge (bread)
  • random electrons with negative charge throughout (raisins)
• Bohr Model (Planetary Model)


  The danish physisicict visualized the electron as rotationg in orbits around the nucleus, like the planet rotating around the sun
• Rutherford's Model (Nuclear Model)



  The atom consists of a dense positive center called nucleus that is orbited by negatively charged electrons