2)Atoms, Ions and Compounds

• Atomic Number

  Indicates the number of protons and electrons within the atoms of an element.
• Electrons

  • Is a charged particle (charge of -1)
  • Mass of 1/1836
  • Electrons are located in electron shells or energy levels
• Ions

  • An ion is created when a neutral atom loses or gains electrons, making them charged.
  • They'll either be an anion to a cation.
• Isotopes

  • Atoms of the same element, within a sample, that have the same amount of protons but different amount of neutrons.
• Neutrons

  • Particles with a mass of 1
  • Have a charge of 0
  • They are located within the nucleus of the atom.
• Protons

  • Are charged particles with a mass of 1
  • Have a charge of +1
  • They are located within the nucleus of the atom.
• Mass Number

  The number that represents the number of protons and neutrons added together.
• Why do atoms have no overall electrical charge?

  Atoms contains the same number of protons (+1 charge) and electrons (-1 charge) so the charges cancel out.
• What is a cation?

  A cation is a positively-charged ion.
• What is an anion?

  An anion isa negatively-charged ion.
• Similarities and differences between atoms and ions of the same element:

  • Have the same number of protons.
  • Have different number of electrons.
• Relative Isotopic Mass

  Relative Isotopic Mass is the mass number of an atom of an isotope when compared with one-twelfth of the mass of an atom of carbon-12.
• Relative Atomic Mass 


  Relative Atomic Mass is the mean mass number of an atom of an element when compared to one-twelfth of the mass of an atom of carbon-12.
• Relative Atomic Mass

  (percentage of abundance x mass number) + (percentage of abundance x mass number) / 100
• Aluminium ion

  Al3+
• Silver ion

  Ag+
• Zinc ion

  Zn2+
• Ammonium ion

  NH4+
• Hydroxide ion 


  OH-
• Sulphate ion 


  SO4 2-
• Carbonate ion 


  CO3 2-
• Nitrate ion


  NO3-
• The uses of a Mass Spectrometer

  • Monitoring breaths of patients during surgery whilst under anaesthetic.
  • Detecting banned substances such as steroids in athletics
  • Analysing molecules in space
  • Detecting trace of toxic chemicals in marine life.
• The stages in a mass spectrometer:

  • Ionisation
  • Acceleration
  • Deflection
  • Detection
• Mass Spectrometer - Ionisation 


  Electrons are shot from the electron gun, which knocks an electron from each atom of the substance.
• Mass Spectrometer - Acceleration

  Negatively charged plate attracts the positive ions; therefore they accelerate.
• Mass Spectrometer - Deflection (Uses a Magnetic Field)

  Higher the mass, the stronger the magnetic field needed to deflect the positive ion to reach the detector.
• Mass Spectrometer - Detection

  • Detected by a detector
  • Each ion is of the same element, but may have different amount of neutrons.
• • Number of peaks (on a mass spectrum) = number of isotopes of the same element.
  • Height of the peaks (on a mass spectrum) = Abundance of the isotope.
• Why do isotopes have identical properties:

  Isotopes have identical properties because they have the same electronic configuration.
• What type of property differs between isotopes?

  Physical Properties
• What does Ar stand for?

  Relative Atomic mass
• What is the difference between the relative isotopic mass and the relative atomic mass?

  Relative isotopic mass is the mass of a single isotope of an element, whilst the relative atomic mass is the weighed mean mass of several isotopes.
• What is an element?

  An element is a substance made up atoms with the same number of protons.
• 4 state symbols:

  • (s) = solid
  • (l) = liquid
  • (g) = gas
  • (aq) = aqueous solution (dissolved in water)
• How to tell whether an equation is balanced:

  A balanced equation should have the same number of atoms on the reactant and product sides of the equation.
• 'What 2 things must be the same in a balanced ionic equation?

  • Same number of atom on the reactant and product sides of the equations.
  • Same total charge on the reactant and product sides of the equations.
• What is a spectator ion?

  A spectator ion is an ion that does not take part in the reaction.
• Steps in obtaining the ionic equations from a balanced symbol equation.

  1. Re-write the balanced equations showing the formula of all aqueous ions present.
  2. Cancel the spectator ions (ions that appear on both sides of the equation)
  3. Check ionic charges balance on both sides.
• Describe the plum pudding model of the atom.

  Negatively charged electrons are evenly dispersed within a ball of positive charge.