topic c2- bonding, structure- properties of matter

• formation of ions

  • made when electrons are transferred
  • charged particles
  • atoms lose or gain electrons to form ions
  • they're trying to get a full outer shell
• formation of ions

  • group 1 elements form 1+ ions
  • group 2 elements form 2+ ions
  • group 6 elements form 2- ions
  • group 7 elements form 1- ions
• covalent (non-metals)=

  sharing electrons- strong bonds
• H-H

  single bond
• N≡N

  triple bond
• ionic (metal + nonmetal)=

  metals give electrons to nonmetal
• electrostatic attraction

  • metal is a positive ion- +
  • nonmetal is a negative ion- -
• metallic (metals)=

  positive ions attracted to delocalised electrons in metal structure- outer shell
• structure

  ion= + in a circle

  delocalised electron= - in the sea

  
• ionic bonding

  • magnesium + chlorine -> magnesium chloride
  • mg2+ cl- cl- = mgcl2
  • electrons transfer:
  • 12 mg= 2, 8, 2- transfers to cl and cl
  • 17 Cl= 2, 8 ,7
  • 17 Cl= 2, 8, 7
• sodium chloride

  
• ionic bonding

  • metal (+ion) + non-metal (-ion)
  • metals give electrons to non-metal
  • electrostatic attraction
• ions

  charged particles made when electrons are transferred
• ionic bonding

  the electrostatic attraction between oppositely charged ions. ionic bonding occurs between positive metal ions and negative non-metal ions.
• three properties of ionic compounds:

  1. giant ionic lattice structure= electrostatic forces of attraction between oppositely charged ions act in all directions
  2. high melting and boiling points= lots of energy needed to overcome the many strong bonds
  3. conduct electricity only when molten or dissolved= ions free to move and carry electric charge
• properties of ionic compounds:

  1. giant ionic lattice structure= electrostatic forces of attraction between oppositely charged ions act in all directions
  2. high melting and boiling points= lots of energy needed to overcome the many strong bonds
  3. conduct electricity only when molten or dissolved= ions free to move and carry electric charges
• limitations of ionic compounds

  • model not to scale
  • no gaps between ions
  • only see outer layer of the compound
• empirical formula

  simplest ratio of ions possible
• covalent bonds

  between atoms are strong. forces between molecules are weak.
• covalent bond

  • a shared pair of electrons between two non-metal atoms
  • it happens in non-metal compounds and in non-metal elements
• molecular formula

  show you how many atoms of each element there are

  NH3
• dot and cross diagrams

  • don't allow relative sizes of atoms or their arrangement in space
• ball and stick diagrams

  • don't show which atoms the electrons in the bonds come from
• displayed formula

  • doesn't show 3d structure
• covalent bonding

  • non-metal
  • share electrons
• simple molecular substances

  • as molecules get smaller, less energy is needed to break weaker forces between them
• simple molecular substances- elements:

  hydrogen:

  
• simple molecular substances- elements:

  oxygen

  
• simple molecular substances- elements:

  chlorine

  
• simple molecular substances- compounds:

  hydrogen chloride- hcl

  
• simple molecular substances- compounds:

  water- h2o

  
• properties of simple molecular substances

  • low melting/ boiling point- mostly gases or liquids at room temperature
  • don't conduct electricity- there are no charged particles to carry charge
• molecular substances

  • molecules are neutral particles made from atoms joined together by covalent bonds
  • a molecular substance is made of many identical molecules that are not joined to each other
  • molecules are often quite small, containing just a few atoms
  • weak forces between molecules are intermolecular forces
• molecular substances

  • have low melting and boiling points, are gases and liquids at room temperature and they are only weak so they are easy to overcome
  • molecules are not bonded to each other
• giant covalent structures

  solids containing atoms which are all bonded to each other by strong covalent bonds, e.g. diamond, graphite, silicon dioxide
• giant covalent structures

  • high melting/ boiling points- lots of energy needed to overcome strong covalent bonds
  • don't conduct electricity- no charged particles to carry charge
• giant covalent structures

  • polymers- very long chains of repeating units
  • they're usually solid at room temperature because they have relatively strong intermolecular forces
• allotropes of carbon- diamond

  • bonding- C atoms form 4 covalent bonds
  • properties- very hard
  • melting point- high
  • conductivity- doesn't conduct electricity
• allotropes of carbon- graphite

  • bonding- C atoms form 3 covalent bonds; no covalent bonds between layers
  • properties- soft, slippery
  • melting point- high
  • conductivity- conducts electricity and thermal energy
• allotropes of carbon- graphene

  • bonding- C atoms form 3 covalent bonds
  • properties- strong, light
  • melting point- high
  • conductivity- conducts electricity