chemistry whole unit YouTube

• Protons


  Positively charged particles in the nucleus of an atom
• Neutrons


  Neutral particles in the nucleus of an atom
• Electrons


  Negatively charged particles orbiting the nucleus of an atom
• The size of the nucleus is tiny compared to the massive size of the electron shells
• Proton charge


  Plus 1
• Electron charge


  Minus 1
• Atomic number


  Equal to the number of protons and electrons in an atom
• Mass number


  Equal to the number of protons plus the number of neutrons
• To find the number of neutrons, mass number minus atomic number
• Calculating relative formula mass

  1. Find the mass of each element from the periodic table

  2. Add up the masses
• Percentage of an element in a compound

  Take the mass of the element and divide by the total mass, then multiply by 100
• Groups on the periodic table

  Indicate the number of electrons on the outer shell
• Periods on the periodic table

  Indicate the number of electron shells
• Drawing the electronic arrangement of an atom

  1. Look at the atomic number to determine the number of electrons

  2. Look at the period to determine the number of shells

  3. Look at the group to determine the number of electrons on the outer shell

  4. Fill the shells starting from the innermost
• Isotopes


  Different versions of the same element with the same atomic number but different mass numbers
• Group 1 metals (alkali metals)


  • Lithium
  • Sodium
  • Potassium
  • Rubidium
  • Cesium
  • Francium
• Group 1 metals


  • Become more reactive as you go down the group
  • React with water to produce a salt and hydrogen gas
• Shielding


  The effect of inner electron shells getting in the way of the outer electrons being pulled in
• Group 7 (halogens)


  • Fluorine
  • Chlorine
  • Bromine
  • Iodine
  • Astatine
• Group 7 halogens


  • Most reactive at the top of the group
  • Generally found as diatomic molecules
• Flame test


  Test to identify positive ions by the colour they produce in a flame
• Reactions with sodium hydroxide

  Test to identify positive ions by the colour of the precipitate formed
• Testing for carbonate ions

  1. Add dilute nitric acid, then observe for carbon dioxide gas

  2. Add silver nitrate, observe colour of precipitate for chloride, bromide or iodide ions
• Testing for sulfate ions

  Add dilute hydrochloric acid, then barium chloride, observe for white precipitate
• Ionic bonding


  Occurs between a metal and a non-metal, forming positive and negative ions that attract each other
• Properties of ionic compounds

  • High melting and boiling points
  • Do not conduct electricity as solids, but do conduct when molten or dissolved
• Covalent bonding


  Sharing of electrons between non-metals
• Properties of simple covalent molecules

  • Low melting and boiling points
  • Do not conduct electricity
• Giant covalent structures


  • Diamond
  • Silicon dioxide
• Properties of giant covalent structures

  • High melting and boiling points
  • Do not conduct electricity
• Measuring rate of reaction

  1. Observe colour change

  2. Collect gas

  3. Measure mass loss
• Collision theory


  Explains how factors like temperature, concentration/pressure, and catalysts affect the rate of reaction
• Catalysts speed up reactions without getting consumed or altered
• Frequency of collisions


  How often particles bump into each other
• Successful collisions


  Collisions that result in a reaction taking place
• Concentration


  The number of particles per unit volume
• Pressure


  The number of particles per unit volume
• At low concentration, there aren't many particles around so it doesn't matter how fast they're moving, they won't find other particles to collide with and react
• At high concentration, there are lots of particles around so they are much more likely to find something to collide with and have a successful collision
• Catalyst


  Speeds up a reaction without getting consumed or permanently altered