Energy, elements and bonding

• Kinetic energy


  Energy of movement; heat
• Potential energy


  Energy possessed because of position; chemical energy
• Metabolism

  • Anabolism
  • Catabolism
• Kinetic energy can be converted to potential energy
• An element is a substance that cannot be broken down to other substances by chemical reactions
• There are 92 naturally-occurring elements
• Each element has a unique symbol, usually from the first one or two letters of the name, often from Latin or German
• Essential elements for life

  • Carbon (C)
  • Oxygen (O)
  • Hydrogen (H)
  • Nitrogen (N)
  • Phosphorus (P)
  • Sulphur (S)
  • Calcium (Ca)
  • Potassium (K)
  • Iron (Fe)
  • Iodine (I)
• Carbon, oxygen, hydrogen, and nitrogen make up 96% of living matter
• Goitre is caused by iodine deficiency
• Atom


  Smallest unit of matter which still retains the properties of an element
• Atom


  • Nucleus = protons(+) and neutrons
  • Electrons (-) in clouds around the nucleus, move very fast
• Helium atom

  • 2 electrons in cloud around nucleus
• Electron


  Subatomic particle with charge of -1 and weight of 1/1840
• Proton

  Subatomic particle with charge of +1 and weight of 1
• Neutron

  Subatomic particle with no charge
• The mass of a proton and neutron is 1.66 x 10^-24 g
• Atomic number


  Number of protons in an atom
• Atomic number


  • Hydrogen 1 proton
  • Carbon 6 protons
• Atomic mass


  Sum of masses of all components (electrons, protons, neutrons) of an atom
• Atomic mass


  • Hydrogen 1 Dalton
  • Carbon 12 Daltons
• Isotopes


  Different mass number, same atomic number. Chemistry identical but different masses.
• Atomic orbitals


  • 1S - 2 electrons
  • 2S - 2 electrons
  • 2P - 6 electrons (total 2 in each)
  • Filled orbitals are more stable than unfilled
• Elements with incomplete valence shells can interact with other elements to form "bonds"
• Unpaired or valence electrons are able to interact with other unpaired electrons to complete the valence shell
• Each orbital contains no more than 2 electrons
• Compound

  Substance consisting of two or more elements in a fixed ratio
• Compound

  • Sodium chloride (NaCl) - equal numbers of chlorine and sodium atoms
• Types of bonds

  • Covalent
  • Hydrogen
  • Ionic
  • van der Waal's
• Covalent bonds

  • Sharing of electrons by two atoms
  • Non-polar covalent bond (equal sharing)
  • Polar covalent bond (not equal sharing)
  • Strong (400kJ/mole)
• Covalent bonds

  • H-H
  • O-H
• Hydrogen bonds

  • Weak compared to covalent or ionic bonds (10-20 kJ/mole)
  • Collectively very strong, e.g. structure of DNA
• Ionic bonds


  • Form when two atoms very different in attraction for valence electrons come together - crystal formed
  • Very strong (700 kJ/mole)
• van der Waal's forces

  • Very weak (0.5 kJ/mole)
  • Very short range
  • Collectively strong
  • Interaction between electron clouds
• Protein folding is held in shape by several interactions
• Proteins


  • pepsin
  • keratin
  • haemoglobin