SCIENCE 4TH QT

• Subatomic particles


  Are the basic building blocks of all matter
• EVERYTHING on Earth is made of atoms, even the air and your body
• Subatomic particles that make up atoms

  • Protons
  • Neutrons
  • Electrons
• Protons


  Have a positive charge, have a mass of one
• Neutrons


  Located in the nucleus, have no charge, have a mass of one (similar to the proton)
• Electrons


  Have a negative charge, orbit the nucleus of the atom, are very small (has basically NO mass)
• In a neutral atom, there are the same number of protons and electrons
• Electron Cloud


  Region that surrounds the nucleus, the area where electrons are found and orbit around the nucleus
• Force that holds all the parts of an atom together

  The electromagnetic force of attraction between the positive protons in the nucleus and the negative electrons orbiting around the nucleus
• Atomic Number


  The number of PROTONS in the atoms of an element, used to identify the element from the Periodic Table
• Atomic Mass Number


  Includes the number of protons and neutrons, since they are the two largest particles in the atom
• The atomic mass number is located in the nucleus
• The atomic number identifies the element, the atomic mass number gives the mass of the element
• Atomic Notation


  Includes the atomic number (top left), the atomic symbol (middle), and the atomic mass number (bottom)
• Compounds


  Contain more than one type of element, usually with a positive or negative charge
• A particle with a neutral charge has the same number of protons and electrons
• Ions


  Atoms that carry a net electrical charge, either positive (cations) or negative (anions)
• Atomic Theory Timeline


  • Democritus (400 BC)
  • John Dalton (1800s)
  • J.J. Thomson (1890s)
  • Ernest Rutherford (1909)
  • Niels Bohr (1913-1915)
  • James Chadwick (1932)
• Democritus believed that the universe was made of tiny uncuttable particles called atoms
• John Dalton proposed the atomic sphere model as the early theory of the atom
• J.J. Thomson discovered the electron and proposed the "plum pudding" model of the atom
• Ernest Rutherford discovered the atom is mostly empty space and that the proton had a positive charge
• Niels Bohr worked with the Quantum Theory and developed the model of the highest energy levels of the atom
• James Chadwick discovered the neutron, the third subatomic particle
• Dmitri Mendeleev published his version of the periodic table in 1869, arranging elements based on increasing atomic weight
• Henry Moseley revised the periodic table in 1918, discovering that atomic number is the most fundamental property of an element, not atomic mass
• Periodic Trends of the Elements

  • Atomic radii
  • Ionic radii
  • Ionization energy
  • Electron affinity
  • Electronegativity
  • Metallic & nonmetallic character
• Atomic radii


  Measured as one half of the distance between the nuclei of two adjacent similar atoms, it measures atomic size
• Ionic radii


  Measured as one half of the distance between the nuclei of two adjacent similar ions, it measures ion size
• Ionization energy


  The energy needed to remove an electron from a free atom in the gas state, it measures how tightly electrons are bound to an atom
• Electron affinity


  The energy released when an electron is added to a free atom in the gas state, it measures how well atoms attract electrons
• Electronegativity


  The electron attracting ability of an atom when it is bonded to another atom
• Metallic character


  The tendency of an element to act as a metal in things such as conductivity, tendency to lose electrons, shininess, malleability and ductility
• Nonmetallic character


  The tendency of an element to act as a nonmetal in things such as conductivity, tendency to gain electrons, cluster and brittleness
• Factors that determine the Periodic Trends of the Elements

  • Number of protons and electrons
  • Distance separating the nucleus and the electrons
  • Pairing of electrons in the outer energy level orbitals
• Atomic size


  Decreases from top to bottom and left to right in the periodic table
• Ionization energy


  Increases from left to right and decreases from top to bottom in the periodic table
• Metallic character


  Increases from top to bottom and decreases from left to right in the periodic table
• Electron affinity


  Increases from left to right and decreases from top to bottom in the periodic table
• Electronegativity


  Increases from left to right and decreases from top to bottom in the periodic table