Topic 3

• Protons


  Positive (+1), located in the nucleus, mass of 1
• Neutrons


  Neutral, located in the nucleus, mass of 1
• Electrons


  Negative (-1), orbit the nucleus in electron shells, very small mass of 0.0005
• Electron configuration


  • First shell can hold 2 electrons, rest can hold 8
  • Protons and neutrons located in the nucleus, most of the mass is here
  • Electrons orbit the nucleus in shells
  • Number of protons and electrons in an atom is always the same, no overall charge
• Atomic number


  • Number of protons each atom has
  • No two elements can have the same amount of protons
  • Located on top of box in periodic table
  • All atoms of a particular element have a certain amount of protons
• Atomic mass


  • Number of protons and neutrons added together
  • Electrons not taken into account due to tiny mass
  • Shown at bottom of boxes in periodic table
• Isotopes


  • Atoms that are different versions of an element
  • Same amount of protons, different amount of neutrons
• Ions


  • Charged particles
  • Net electric charge due to losing/gaining electrons
  • Cations are positively charged (more protons than electrons)
  • Anions are negatively charged (less protons than electrons)
• Groups in periodic table

  • Group 1 - Alkali metals
  • Group 2 - Alkaline earth metals
  • Group 7 - Halogens
  • Group 8 or 0 - Noble gases
• Groups and periods in periodic table

  • Group goes vertically down, tells number of electrons in outer shell
  • Period goes horizontally across, tells number of shells
• Group 1 are the alkali metals
• Group 2 are the alkaline earth metals
• Group 7 are the halogens
• Group 8 or 0 are the noble gases, they are very unreactive as they have a full outer shell of electrons