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• Chemical bond


  Electrostatic force of attraction that holds two or more atoms, ions, molecules or any combination of these together
• Ionic bond


  Formed between a metal and non-metal
• Covalent bond


  Formed between two non-metals
• Noble gases


  • Gaseous elements found in group 18
  • Atoms have stable electronic configuration with completely filled valence shell
• Stable noble gas structure

  Either duplet (2, first shell only) or octet (2,8)
• How atoms not noble gases achieve stable noble configuration

  • Losing or gaining valence electrons (ionic bonding)
  • Sharing valence electrons (covalent bonding)
• Ionic bonding


  Occurs between metal and non-metal where metal atoms lose electrons to form positively charged ions (cations) and non-metal atoms gain electrons to form negatively charged ions (anions) to achieve stable noble configuration
• Ionic bonds


  Strong electrostatic force of attraction between oppositely charged ions
• Formation of ions from atoms

  • Metals usually form cations
  • Non-metals usually form anions
• Cation naming


  Cations have the same name as their elements
• Anion naming


  Anions are named by taking the elemental name and removing the ending and adding "ide"
• Dot-cross diagram


  Represents the number of electrons lost by metal cations and gained by non-metal anions
• Important polyatomic ions


  • Ammonium, NH4+
  • Hydroxide, OH-
  • Nitrate, NO3-
  • Sulfate, SO42-
  • Carbonate, CO32-
  • Phosphate, PO43-
• Ionic compound naming


  First part of name comes from cation, second part comes from anion
• Formulas of common cations

  • Groups 1, 2, 13 metals form cations with 1+, 2+, 3+ charges respectively
  • Transition metals can form cations with different charges
  • Zinc and silver normally form 2+ and 1+ ions respectively
  • Ammonium is a polyatomic cation with 1+ charge
• Formulas of common anions

  • Groups 15, 16, 17 elements form anions with 3-, 2-, 1- charges respectively
  • Sulfate, nitrate, carbonate, phosphate, hydroxide are polyatomic anions
• Chemical formula of ionic compound

  1. Identify relevant ions

  2. Cross multiply charges to get number of cations and anions

  3. Electrons lost by metal atoms are transferred to non-metal atoms
• Structure of ionic compound

  Giant lattice structure with oppositely charged ions arranged in 3D, held together by strong ionic bonds
• Covalent bonding

  Electrostatic force of attraction between shared pair of electrons and positively charged nuclei of both atoms
• Covalent molecule

  Two or more atoms become covalently bonded to form a molecule
• Common diatomic gases


  • H2, O2, N2, F2, Cl2, Br2
• Drawing simple covalent molecule

  1. Determine central atom

  2. Determine number of valence electrons

  3. Join central atom to surrounding atoms with appropriate number of bonds
• Types of covalent structures

  • Simple molecular
  • Giant molecular
• Producers


  Able to synthesize complex organic substances from simple inorganic substances using light or chemical reactions
• Consumers


  Unable to synthesize complex organic substances, feed on complex organic substances made by producers
• Decomposers


  Act on dead organisms, break down organic matter into simple inorganic matter to be available for other organisms, recycle nutrients
• Nutrient cycle


  Nutrients being moved and exchanged from one organism to another in closed loops
• Nitrogen cycle


  1. Describes the circulation of nitrogen between plants, animals, atmosphere and soil

  2. Bacteria help change nitrogen between forms so it can be absorbed and used by plants
• Overuse of chemical fertilizers (nitrogen)


  Causes water pollution
• Eutrophication


  1. Excessive nutrients (nitrates) from fertilizers and sewage enter water system

  2. Algae grows rapidly, blocking light to submerged plants

  3. Decomposers multiply rapidly using up oxygen, causing other organisms to die
• Inorganic waste and insecticides can be dumped into water bodies, accumulating in high concentrations in aquatic organisms through bioaccumulation and biomagnification
• Plastics are non-biodegradable, can be eaten or cause entanglement in animals, and release toxins when broken down into microplastics that enter the food chain
• Carbon sinks


  Absorb and store carbon compounds for an indefinite period, removing more carbon than they release
• Carbon sinks


  • Forests
  • Oceans
• Carbon cycle


  1. Constant exchange of carbon between abiotic and biotic environment

  2. Carbon dioxide removed from atmosphere through photosynthesis and dissolved in oceans

  3. Carbon returned to atmosphere through respiration, decomposition, and combustion of fossil fuels
• Greenhouse gases (carbon dioxide and methane) in the atmosphere have increased rapidly, causing global warming and climate change
• Acid


  Substance that forms hydrogen ions (H+) when dissolved in water
• Common acids


  • Hydrochloric acid (HCl)
  • Nitric acid (HNO3)
  • Sulfuric acid (H2SO4)
  • Phosphoric acid (H3PO4)
  • Ethanoic acid (CH3COOH)
• Alkali


  Substance that forms hydroxide ions (OH-) when dissolved in water
• Common alkalis


  • Sodium hydroxide (NaOH)
  • Potassium hydroxide (KOH)
  • Calcium hydroxide (Ca(OH)2)
  • Aqueous ammonia (NH3)