Atomic structure chp3

• Subatomic Particles contain:


  • Proton
  • Neutron
  • Electron
• The total relative mass of an atom is determined by the Proton and Neutron only
• Since most of the atom's mass is determined by the nucleus, most of the atom is empty space
• Relative Charge


  • Proton is +1
  • Electron is -1
  • Neutron is 0
• Number of Protons is always equal to electrons, but may have differing numbers of Neutrons in an atom
• An atom is electrically neutral-number of protons always the same as number of electrons
• Relative atomic mass (Ar)


  The average mass of one atom of an element compared to the mass of one carbon-12 atom
• Isotopes


  Atoms of the same element, with the same number of protons and electrons but different numbers of neutrons
• All isotopes of the same element have the same chemical properties but slightly different physical properties
• Proton Number


  Always the smaller number, also known as atomic number, unique to the atom itself
• Nucleon


  Protons + Neutrons in the nucleus
• Nucleon Number


  Total number of protons and neutrons in the nucleus, also known as mass number
• The periodic table shows the proton number placed above the atomic symbol
• Ion


  Particle formed when atom/group of atoms gain/lose electrons, number of protons & neutrons remain the same, charge number indicates amount of electrons gained or lost
• Electron Shells


  Innermost shell lowest energy, outermost shell highest energy, first shell max 2 electrons, second and third max 8 electrons each, outermost shell are valence electrons
• Electronic Configuration


  noted as, e.g. 2.2 or 2,2 (beryllium atom)
• Number of electrons = Proton Number
• Atoms become Ions when


  • Lose electrons (positive ions/cations)
  • Gain electrons (negative ions/anions)
• Metal elements lose electrons, non-metal elements gain electrons
• • Group 14 atoms do not lose/gain electrons, they share electrons
  • Group 18 atoms do not lose/gain electrons, they have a full valence shell
• Atoms aim to be stable by having a full valence shell
• Relative mass of:

  proton+neutron=1

  electron=1/1840
• Nuclide notation

  • larger number is always nucleon number (mass number)
  • smaller number is always Proton number (atomic number)