IGCSE chemistry topics 8 and 9

• Metals are found at the left and centre of the periodic table
• In metallic bonding, the outer electrons separate from their atoms and become delocalized, creating a 'sea of electrons' that the positive metal ions are attracted to
• Properties of metals include:

  • Forming crystals called grains in a tightly packed and denser lattice
  • Having high melting and boiling points due to strong metallic bonds
  • Being good conductors of heat and electricity, with silver being the best conductor of electricity and copper the second best
  • Being tough and not brittle, with layers of the lattice sliding over each other without breaking due to the free movement of electrons
• Metals are malleable (can be bent and pressed into shape) and ductile (can be drawn into wires)
• Grain boundaries are where one metal grain meets another, affecting the strength of the metal
• Alloying is the process of making metals stronger by adding another element when the metal is molten, creating an alloy
• Different elements added to metals create different alloys with varied properties, like adding zinc, magnesium, and copper to aluminum to create a light but strong alloy used in aircraft construction
• Alloys like stainless steel (iron with chromium and nickel) and solder (tin and lead) have specific uses due to their properties
• Corrosion is the gradual destruction of a metal due to reactions with other chemicals in its environment, with rusting being a type of corrosion affecting iron and steel
• Solutions to corrosion include painting, oiling, greasing, coating with plastic, galvanization, and sacrificial protection using a more reactive metal to protect a less reactive one
• The reactivity series is a list of metals placed in order of their reactivity, used to predict reactions with oxygen, water, and acids
• Metals can be extracted from ores through reduction with carbon or electrolysis, with electrolysis being used for reactive metals like aluminum found in bauxite
• The Periodic Table arranges elements in periods and groups in order of increasing proton number/atomic number, with metals on the left and centre, non-metals on the right (except hydrogen), and metalloids between metals and nonmetals
• The Periodic Table is an arrangement of elements in periods and groups in order of increasing proton number/atomic number
• Metals are located on the left and center, non-metals on the right (except hydrogen), and metalloids between metals and nonmetals
• Solids are found on the left, in the center, and on the right of the Periodic Table, while liquids are in the middle and on the right
• Gases are located on the far right of the Periodic Table
• The only two liquids on the Periodic Table are bromine and mercury
• Groups in the Periodic Table indicate the number of electrons in the outer shell/valence electrons, while periods indicate the number of shells in the element
• Trends in Groups: the number of outer shell electrons is the same, and the number of complete electron shells increases by one
• Alkali Metals (Group 1) have 1 electron in their outer shell, making them easily lose this electron in reactions to form positive ions with a +1 charge
• The reactivity of alkali metals increases down the group due to the size of the element’s atoms and the number of full electron shells increasing down the group
• General properties of Alkali Metals: softness increases down the group, low density, low melting and boiling points, good conductors of heat and electricity, and shiny appearance when freshly cut
• Reactions with water: All alkali metals react readily with water, becoming more vigorous down the group and creating alkaline hydroxide ions
• Halogens (Group 7) have 7 electrons in their outer shell, gaining 1 electron in reactions to form negative ions with a -1 charge
• Reactivity of halogens decreases down the group due to the size of each element’s atoms and the number of full electron shells increasing down the group
• Halogens exist as diatomic molecules (F2, Cl2, Br2, I2) and are non-metals that do not conduct electricity, are brittle, poisonous, and smelly
• When halogens react with another substance, they become ions called halides, and a more reactive halogen will displace a less reactive halide from its compounds in solution
• Transition metals form positive ions when they react, have variable valency, are hard, strong, and have a high density, and are less reactive than alkali metals
• Noble gases are monoatomic, colorless, inert due to full outer shell electrons, and have increasing density, melting point, and boiling point down the group
• Process of extracting iron:

  1. Hot air reacts with coke to produce carbon dioxide and heat energy to heat up the furnace: C(s) + O2(g) → CO2(g)

  2. More coke is added to the furnace to reduce carbon dioxide into carbon monoxide, a good reducing agent: CO2(g) + C(s) → 2CO(g)

  3. Iron(III) oxide is reduced by carbon: 2Fe2O3(s) + 3C(s) → 4Fe(l) + 3CO2(g)

  • In this reaction, iron(III) oxide is reduced to iron, and carbon is oxidised to carbon dioxide
  • In the blast furnace, carbon monoxide can be used instead of carbon to reduce iron(III) oxide: Fe2O3(s) + 3CO(g) → 2Fe(l) + 3CO2(g)
• Metal ions from a lattice which is more tightly packed and denser than the lattices in ionic compounds
• What is metallic bonding?

  electrostatic attraction between positive metal ions and a sea of delocalized electrons.
• Reactions with metals and oxygen:

  Metal(s) + Oxygen(g) → Metal Oxide
• Reactions with metals and Acids:

  Metal(s) + acid → Metal salt + Hydrogen (g)
• The formula of Iron rusting: 4Fe+3O2 → Fe2H2O4 / Iron + Water + Oxygen → Hydrated iron ( III) oxide
• Why are most alloys stronger than their pure counterparts? 

  The atoms in pure iron are arranged in densely-packed layers. These layers can slide over each other. This makes pure iron a very soft material.

  The atoms of other elements are different sizes. When other elements are added to iron, their atoms distort the regular structure of the iron atoms. 

  It is more difficult for the layers of iron atoms in steel to slide over each other and so this alloy is stronger than pure iron.
• What is a Metalloid?

  chemical elements whose physical and chemical properties fall in between the metal and non-metal categories.
• Describe the relationship between an elements Valency electrons and the type of element it is:

  The Valency of an element is the tendency of their atoms to lose or gain a certain number of electrons to complete the Octet rule (gain a full outer shell). We can understand that those who are losing their valence electrons are metals and those that are attempting to gain a valence electron are non-metals. Its tendency to lose or gain valence electrons affects the element's melting point, boiling point and overall its reactivity.
• Lithium reacts with water:

  Lithium is the least reactive of the alkali metals. When added to water, it fizzes and moves around slowly across the surface of the water.