ATOM

• Dalton's atomic theory
• Elements are composed of extremely small particles called

  atoms
• all atoms of a given element are 


  identical
• the atoms of one element are ___ from the atoms of other elements

  different
• are composed of atoms of more than one element

  compound
• in any compound, the ratio of the numbers of atoms of any two of the elements present is either 


  an integer or a simple fraction
• a chemical reaction involves only the:

  separation, combination, or rearrangement of atoms
• a chemical reaction does not involve the

  destruction or creation of atom
• a nuclear particle with a positive charge


  proton
• a proton has a mass more than 1800 times that of the ___

  electron
• it has a mass almost identical to that of the proton

  neutron
• it has no electric charge

  neutron
• negatively charged particle


  electron
• it exists in the region around the nucleus


  electron
• it is an atom's central core; contains most of the atom's mass

  nucleus
• a nucleus is positively charged
• nuclide is an atom characterized by a ___ atomic and mass number

  definite
• cation


  positive
• anion


  negative
• number of protons in the nucleus of an atom

  atomic number
• total number of protons and neutrons in a nucleus

  atomic mass
• ak.a. atomic weight


  atomic mass
• atoms with the same atomic number but different mass numbers


  isotopes
• in an isotope, the nucleus has the same number of protons but different number of neutrons
• exactly 1/12 the mass of a carbon-12 atom

  atomic mass unit
• it is expressed in atomic mass units

  atomic mass
• an aggregate of at least two atoms

  molecule
• a molecule containing two atoms

  diatomic
• elements that exist as diatomic molecules are H, N, O, F, Cl, BR, and I
• a molecule containing more than one atoms

  polyatomic
• an electrically charged particle obtained by either losing or adding an electron

  ion
• an ion formed from a single atom

  monoatomic ion
• an ion formed from more than one ion carrying a net electric charge

  polyatomic ion
• as the period number increases, there is an increase in the number of main energy levels


  atomic size or radius
• energy required to remove a single electron from the highest or outermost energy level of an ion or a gaseous element

  Ionization energy
• Ionization energy: as atoms become larger, ionization energy decreases [INVERSE PROPORTION]
• energy released when an electron is added to an isolated atom in its ground state


  electron affinity
• Electron affinity:

  increases in magnitude from left to right across the period, except the noble gases
• the ability of an atom to attract electrons


  electronegativity
• electronegativity: the smaller the atom, the greater is its ability to attract an electron