CHEMISTRY-Atoms, Elements and Ions

• Everything whether it's living, non-living or even a cell itself is made up of lots of tiny particles which we call atoms
• A single cell probably contains more than 100 trillion atoms
• Atom


  Basic structure is a central nucleus surrounded by electrons which orbit around the nucleus in rings that we call shells
• Particles that make up the nucleus

  • Protons
  • Neutrons
• Protons and neutrons


  • Have the same mass, with a relative mass of 1
  • Protons have a positive charge of 1+
  • Neutrons have no charge (are neutral)
• Electrons


  • Have a mass 2000 times smaller than protons and neutrons
  • Have a negative charge of 1-
• The size of an atom depends on which element it is
• Atoms have a radius of around 0.1 nanometers
• Most of an atom is actually empty space
• The nucleus is 10,000 times smaller than the width of the atom
• Electrons are even smaller than the nucleus and would be too small to see in the atom diagram
• Ion


  An atom that has lost or gained electrons, so the positive and negative charges no longer balance
• Ions


  • One minus negative ion (one extra electron)
  • Two minus negative ion (two extra electrons)
  • One plus positive ion (one less electron)
• The periodic table represents different types of atoms, which we call elements
• Atomic number


  Tells us how many protons the atoms of that element have
• Mass number


  Tells us the total number of neutrons and protons in that atom
• The number of protons and electrons in an atom is always the same
• Atom


  Central nucleus comprising protons and neutrons, with electrons orbiting the nucleus
• Protons


  Determine which element the atom is
• Hydrogen


  • Smallest element, with 1 proton and 1 electron
• There are around 100 different elements
• Periodic table


  Organizes elements into boxes, each representing a different element
• Nuclear symbol


  The one or two letter symbol representing the element name
• Atomic number


  The number of protons in the atoms of that element
• Atoms with the same number of protons are the same element
• Isotopes


  Different forms of the same element that have the same number of protons but a different number of neutrons
• Relative atomic mass


  The average mass of all the isotopes that make up a particular element
• Calculating relative atomic mass

  Multiply each isotope's abundance by its mass, sum these, then divide by the sum of all isotope abundances
• The relative atomic mass of copper is 63.6