chemistry mock

• Metals appear on the left side of the periodic table, whereas non-metals appear on the right
• Metals

  • Conducts electricity
  • Conducts heat
  • High melting point
  • High boiling point
  • Malleable
  • Can be hammered into sheets
  • Ductile
  • Can be drawn out into wire or threads
  • Lustrous / Shiny
• Non-metals

  DOES NOT conduct electricity

  DOES NOT Conduct heat

  Low melting point

  Low boiling point

  Non-malleable

  Brittle

  Breaks or fractures easily

  Dull
• metals behave differently to non-metals and compounds due to their metallic bonding.
• The properties of all materials, are determined by:

  • the types of atoms present
  • the types of bonding between the atoms
  • the way the atoms are packed together
• Metals are giant structures with a “sea” of free electrons. Metallic bonds are strong, so metals can maintain a regular structure and usually have high melting and boiling points.
• Outer shell electrons of metals are free to move. The strength of a metallic bond is the force of attraction between the metal ions and free moving electrons.
• The more free electrons and more protons the ions possess, the stronger a metal becomes.
• Because these “free” (or delocalised) electrons are free to move about the metallic structure, this allows metals to conduct electricity and conduct heat.
• The more free electrons a metal has, the better it is at conducting both electricity and heat.
• Metals are also malleable (hit into shape) and ductile (drawn into wires) because the free electrons allow the metal atoms to slide over each other
• Metallic bonds are strong and a lot of energy is needed to break them. This is why metals have high melting points and boiling points
• As the number of free electrons increase, i.e. move across the periodic table from left to right, so too does the melting and boiling points. This is because of the increased attraction between the positive ions and the free electrons.
• When a chemical reaction takes place, new bonds are formed.
• Ionic compounds form by the transfer of electrons from a metal to a non-metal atom. Charged particles called ions are formed.
• Covalent bonding occurs between 2 or more non-metals. When these bonds form, the atoms share electrons.
• Charged particles called ions are formed when electrons are transferred between atoms during chemical bonding.
• When sodium chloride (NaCl) forms, one electron is transferred to chlorine. This will form a full stable outer shell (like noble gasses) for the two particles.
• When hydrogen gas (H2) forms, electrons are shared between two atoms to form a molecule. These molecules are neutral (no charge).
• There are many ionic bonds in an ionic compound such as sodium chloride, arranged in giant lattice structures.
• Ionic compounds have high melting and boiling points because of the strength of the electrostatic forces of attraction between oppositely-charged ions.
• The oppositely-charged ions are arranged in a regular way to form a giant ionic lattice.
• It is a 'lattice' because the arrangement is a regular one and 'giant' because the arrangement is repeated many times with large numbers of ions
• Ionic compounds often form crystals as a result.
• The number of ions in an ionic compound is such that the overall charge of a sample of the compound is zero.
• For an ionic substance to conduct electricity, its ions must be free to move so that they can carry charge from place to place.
• Ions are free to move when an ionic compound is a molten liquid or in solution but not when it is solid.
• The melting point of sodium chloride is lower than that of magnesium oxide because it has weaker ionic bonds, which need less heat energy to break/overcome.
• 1. The Na+ and Cl– ions in sodium chloride have fewer charges than the Mg2+ and O2– ions in magnesium oxide.
  2. Na+ ions are larger than Mg2+ and cannot get as close to the negatively charged ions
• Simple molecules consist of a small number of atoms joined by covalent bonds. For example, water and carbon dioxide exist as simple molecules.
• The covalent bonds binding the atoms together are very strong but there are only very weak forces holding the molecules to each other (the intermolecular forces).
• Therefore, only a low temperature is needed to separate the molecules when they're melted or boiled.
• This means that compounds that have simple molecular structures have low boiling and melting points. There are no free electrons to carry an electrical current, so simple molecular structures do not conduct electricity
• They contain a lot of non-metal atoms, each joined to adjacent atoms by covalent bonds. Their atoms are arranged into giant lattices, which are strong structures because of the many bonds involved.
• Substances with giant covalent structures have very high melting points, because a lot of strong covalent bonds must be broken.
• Diamond is a form of carbon in which each carbon atom is joined to four other carbon atoms, forming a giant covalent structure. As a result, diamond is very hard and has a high melting point, over 3500ºC.
• Diamond:

  It does not conduct electricity.

  Appearance - Transparent/crystalline.

  Uses - Gemstones, Glass cutting, Drill bits.
• Graphite is a form of carbon in which the carbon atoms form layers. Each carbon atom in a layer is joined to only three other carbon atom
• The fourth electron of each carbon atom becomes delocalised between the layers. This is why graphite conducts electricity.
• The layers can slide over each other because there are no covalent bonds between them. This makes graphite much softer than diamond. It is used in pencils and as a lubricant.