atomic structure and isotopes

• Atom


  The building blocks of all matter, made from protons, neutrons, and electrons. Atoms have no overall charge
• Ion


  An atom or group of atoms with an overall charge
• Atoms become ions


  The loss or gain of electrons can provide electronic stability by creating a full outer energy level (the number of protons and neutrons does NOT change)
• Proton


  A subatomic particle found in the nucleus of the atom with a relative mass of 1 and a relative charge of +1
• Neutron


  A subatomic particle found in the nucleus of the atom with a relative mass of 1 and a relative charge of 0
• Electron


  A subatomic particle found in the energy levels/shells around the atom, with a relative atomic mass of 1/1836, and relative charge of -1

  
• Atomic number


  Number of protons in the atom
• Mass number


  The number of protons + the number of neutrons in the atom
• Isotope


  Atoms of the same element containing different numbers of neutrons
• Isotopes


  • They have the same chemical properties and same physical properties, but different masses
• Element


  A substance containing only one type of atom
• Molecule


  A small group of covalently bonded atoms
• Compound


  A substance containing more than one type of atom which are chemically combined
• Mixture


  A substance containing more than one type of element or compound which are not chemically combined
• Polyatomic


  Many atoms in the ion
• Formulae for ionic compounds

  • Carbonate ion- CO3^2-
  • Sulfate ion- SO4^2-
  • Nitrate- NO3^-
  • Phosphate- PO4^3-
  • Ammonium- NH4^+
  • Hydroxide- OH-
  • Cyanide- CN-
  • Hydronium- H3O+
• Subatomic particles


  Particles that make up an atom
• Nucleus


  • Located in the centre of the atom, made up of protons and neutrons
• Area outside of the nucleus


  • Comprises of shells/energy levels, and contain electrons
• Atoms must have the same number of protons and electrons to balance the charge
• Atomic number


  The number of protons tells you which atom it is, as each atom has a different number of protons
• Mass number


  The number of protons and neutrons present
• Number of shells/energy levels

  Tells you its period number (row it is in)
• Number of electrons in the outer shell

  Tells you its group (column) number
• Relative atomic mass


  The weighted mean mass of an atom compared to 1/12 of the mass of an atom of carbon-12

  
• Relative isotopic mass


  The mass of an isotope of an atom compared to 1/12 the mass of an atom of carbon-12

  
• Relative molecular mass (Mr)


  The weighted mean mass of a molecule compared to 1/12 of the mass of an atom of carbon-12
• Relative formula mass (Mr)


  The weighted mean mass of a formula unit compared to 1/12 of the mass of an atom of carbon-12

  
• Determination of Relative Atomic Mass by Mass Spectrometry

  1. Sample enters mass spectrometer

  2. Bombarded with electrons to produce positive 1+ ion

  3. Mass spectrometer measures mass:charge ratio

  4. Peaks on graph show isotopic composition

  5. Equation to work out relative isotopic mass

  
• Relative atomic mass (RAM)

  If both isotopes are present in equal amounts, RAM would be in the middle. As RAM is closer to 11, B-11 is more abundant

  
• Calculating the % abundance of isotopes from the relative atomic mass

  1. Work out the difference between the isotopes in terms of mass

  2. Work out the difference between each isotope's mass and the RAM

  3. For the more abundant isotope, do the difference between its mass and the RAM over the overall difference in mass, then times by 100

  4. For the less abundant isotope, remainder of the difference between the more abundant mass and the RAM /the overall difference, then timesed by 100