C1

• 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 structure


  • Central nucleus surrounded by electrons which orbit around the nucleus in rings that we call shells
• Protons


  Particles in the nucleus, have a positive charge
• Neutrons


  Particles in the nucleus, have no charge
• Electrons


  Particles orbiting the nucleus, have a negative charge
• Protons and neutrons have the same mass, with a relative mass of 1
• Electrons have a mass 2000 times smaller than protons and neutrons
• The size of an atom depends on which element it is, generally around 0.1 nanometers in radius
• Most of an atom is empty space, like the solar system with a central nucleus and orbiting electrons
• The nucleus is 10,000 times smaller than the width of the atom
• The number of protons and electrons in an atom is equal, making the atom overall neutral
• Ion


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


  • One minus negative ion
  • Two minus negative ion
  • One plus positive ion
• Periodic table


  Each box represents a different type of atom, called an element
• Elemental symbol


  One or two letter symbol that represents an element
• Atomic number


  Number of protons in the atom, determines the element
• Mass number


  Total number of neutrons and protons in the 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, each box represents a different element
• Nuclear symbol


  Represents an element
• Atomic number


  Unique number representing the number of protons in an element
• An atom with 3 protons cannot be carbon, it must be the element with atomic number 3, which is lithium
• Element symbol


  One or two letter symbol representing the element name (e.g. C for carbon, Li for lithium)
• Some element symbols are more confusing (e.g. sodium is Na, iron is Fe)
• 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

  1. Multiply each isotope's abundance by its mass

  2. Sum the results

  3. Divide by the sum of the abundances of all isotopes
• The relative atomic mass of copper is 63.6
• Transition elements


  • They are metals
  • They have high melting points and densities
  • They are strong and hard
  • They form coloured compounds
  • They act as catalysts
• Chemical properties


  How a substance reacts with other substances
• Transition elements vs group 1 elements

  Transition elements react slowly or not at all with oxygen at room temperature, while group 1 elements react quickly
• Reaction of copper with oxygen

  Copper + oxygen → copper oxide
• Transition elements vs group 1 elements with water

  Most transition elements react slowly or not at all with cold water, while group 1 elements react vigorously
• Iron reacts with water and oxygen at room temperature to form hydrated iron(III) oxide, or rust
• Transition elements vs group 1 elements with halogens


  Some transition elements react with halogens, while group 1 elements react vigorously