chemistry

• Atom


  The smallest particle which can exist on its own
• Sub-atomic particles


  • Protons
  • Neutrons
  • Electrons
• Nucleus


  The centre of an atom, contains protons and neutrons
• Particle properties


  • Proton: Relative mass 1, Relative charge +1, Location in atom: Nucleus
  • Neutron: Relative mass 1, Relative charge 0, Location in atom: Nucleus
  • Electron: Relative mass 1/1840, Relative charge -1, Location in atom: Shells
• Element


  A substance that is made up of only one type of atom
• There are many elements in the periodic table
• Compound


  Consists of two or more elements, chemically bonded together
• Compounds ending in 'ide' contain only two elements
• Compounds ending in 'ate' also contain oxygen
• Compounds containing specific elements

  • Lead and bromine: Lead Bromide
  • Sodium, carbon and oxygen: Sodium Carbonate
  • Lithium, oxygen and hydrogen: Lithium Hydroxide
  • Iron and chlorine: Iron Chloride
  • Silver, nitrogen and oxygen: Silver Nitrate
  • Aluminium and oxygen: Aluminium Oxide
• How elements combine to form compounds

  1. Hydrogen + Chlorine → Hydrogen Chloride

  2. Iron + Sulfur → Iron Sulfide

  3. Magnesium + Oxygen → Magnesium Oxide

  4. Calcium + Bromine → Calcium Bromide
• Atomic number (Z)


  The number of protons in an atom of that element
• Mass number (A)


  The number of protons and neutrons in the nucleus of an atom of that element
• Protons, neutrons, electrons


  Number of protons = atomic number

  Number of electrons = atomic number (as atoms are neutral)

  Number of neutrons = mass number - atomic number
• Example elements and their properties

  • Hydrogen: 1 proton, 0 neutrons, 1 electron

  Carbon: 6 protons, 6 neutrons, 6 electrons

  Oxygen: 8 protons, 8 neutrons, 8 electrons

  Potassium: 19 protons, 20 neutrons, 19 electrons

  Silver: 47 protons, 60 neutrons, 47 electrons

  Lead: 82 protons, 125 neutrons, 82 electrons

  Barium: 56 protons, 81 neutrons, 56 electrons

  Iron: 26 protons, 30 neutrons, 26 electrons

  Mercury: 80 protons, 121 neutrons, 80 electrons

  Calcium: 20 protons, 20 neutrons, 20 electrons

  Iodine: 53 protons, 74 neutrons, 53 electrons

  Uranium: 92 protons, 146 neutrons, 92 electrons
• Nucleus


  Small, dense, positively charged centre of atom, composed of protons and neutrons
• Electrons


  Found in shells, orbiting the nucleus
• How electrons fill the shells

  Electrons fill the first shell first

  Once first shell is full, they fill the second shell

  First shell can hold 2 electrons, other shells can hold 8 electrons

  Electrons will only fill into a new shell when the previous shell is already full
• Group number


  Tells us the number of electrons in the outer shell
• Period number


  Tells us the number of shells the atom has
• Atom


  Has no electronic charge, as it has an equal number of protons and electrons
• Ion


  A charged particle, formed when an atom gains or loses an electron
• Formation of ions


  Group 8 elements have full outside shells (Noble Gases)

  An ion is an atom that has lost or gained electrons
• Examples of ions


  • Hydrogen: 0 electrons, +1 charge

  Lithium: 2 electrons, +1 charge

  Nitrogen: 10 electrons, -3 charge

  Oxygen: 10 electrons, -2 charge

  Neon: 10 electrons, 0 charge

  Sodium: 10 electrons, +1 charge

  Calcium: 18 electrons, +2 charge

  Zinc: 28 electrons, +2 charge

  Copper (I): 28 electrons, +1 charge

  Fluorine: 10 electrons, -1 charge

  Aluminium: 10 electrons, +3 charge
• Isotope


  An atom with the same number of protons and electrons, but different numbers of neutrons
• Isotopes have the same chemical properties but different physical properties
• Relative atomic mass


  The average mass number for a sample of an element
• The relative atomic mass of chlorine is 35.5 because the naturally occurring sample contains 75% chlorine-35 and 25% chlorine-37</b>
• Bonding


  The joining of atoms together
• Types of bonding


  • Ionic
  • Covalent
  • Metallic
• Bonding processes


  • Atoms try to obtain a stable arrangement
  • Atoms try to possess a full outer shell of electrons
  • Atoms do this by transferring or sharing electrons
• The Noble Gases all have a full outer shell of electrons. They do not need to gain or lose any electrons, as they already have a stable arrangement
• Ion


  A charged particle formed when an atom gains or loses electrons
• Molecular ion


  A charged particle containing more than one atom
• Molecular ions


  • NH4+
  • OH-
  • SO42-
  • SO32-
  • NO3-
• Ionic bonding


  Occurs when a metal transfers one or more electrons to a non-metal, producing positive and negative ions
• The purpose of bonding is for the atom to gain a full outer shell of electrons
• Atoms want a full outer shell as it is a stable arrangement
• When atoms transfer electrons they obtain a more stable arrangement, like their nearest noble gas
• Ionic bonding


  • Sodium ion (positive charge) and chloride ion (negative charge) are attracted because they have opposite charges
  • Ions are held together by a strong electrostatic bond
  • A large amount of energy is required to break this bond