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• Elements


  • There are 118 elements
  • 98 are naturally occurring
  • 20 are synthetically made
• Hydrogen


  The most abundant element in the universe (75%)
• Atom


  • Basic unit of an element
  • Contains 3 subatomic particles: protons, neutrons, electrons
• Atomic nucleus


  • Small, dense region consisting of protons and neutrons as the center of an atom
  • Discovered in 1911 by Ernest Rutherford based on the 1909 Geiger-Marsden gold foil experiment
• Atomic number


  Number of protons or number of electrons in a neutral atom
• Atomic mass


  Sum of protons and neutrons
• Chemical symbol


  Shorthand way of representing the elements (e.g. Hydrogen (H), Carbon (C), Oxygen (O), Nitrogen (N))
• Dmitri Mendeleev


  • Arranged the periodic table of elements
  • Chief architect of the periodic table
• Periodic table of elements

  • Provides a systematic and logical arrangement of the chemical elements
  • Elements are organized into horizontal rows (periods) and vertical columns (groups)
• Hays-McDaniel Line


  • Heavy zigzag stair step line in the periodic table
  • Left of the line is the region where metals are located
  • Right of the line are non-metals
  • Elements along the line are metalloids
• Properties of Metals


  • Solid (except mercury)
  • Hard (except lithium, potassium and sodium)
  • Shiny luster
  • Best conductors of heat
  • Good conductors of electricity
  • Malleable
  • Ductile
  • High melting point
  • Very dense
• Examples of Non-Metals


  • Solids: carbon, sulfur, phosphorus
  • Liquid: bromine
  • Gases: oxygen, hydrogen, nitrogen
• Bromine


  • Used in many areas such as agricultural chemicals, dyestuffs, insecticides, pharmaceuticals and chemical intermediates
  • Some uses are being phased out for environmental reasons, but new uses continue to be found
  • Bromine compounds can be used as flame retardants
• Properties of Non-Metals


  • Dull luster
  • Insulators (do not conduct electricity or heat well)
  • Soft and brittle (except for diamonds)
• Metalloids


  • Usually considered under this classification are the chemical elements boron, silicon, germanium, arsenic, antimony and tellurium
  • The rare elements polonium and astatine are also sometimes included
  • Elements classified as metalloids have physical properties of both metals and non-metals
  • Some are shiny, some are dull, they are somehow malleable and ductile, and can conduct heat and electricity at a lesser level than metals
  • Some metalloids are useful semiconductors, which are used in electronics
• Compound


  • Forms when two or more different elements join together chemically in definite proportion by mass
  • Has its own unique and definite physical and chemical properties
• Molecule


  • Smallest unit of a compound
  • Compounds can only be separated using chemical methods
• Electrolysis of water


  Decomposition of water into oxygen and hydrogen gas due to an electric current being passed through the water
• Chemical bonds


  Forces that hold atoms together to make compounds or molecules
• Classifications of Compounds


  • Organic compounds (from living organisms, composition: carbon)
  • Inorganic compounds (from non-living things, composition: metal and other elements)
• Acid


  Substance that releases H+ ions in an aqueous solution (aqueous means water)
• Strong acid


  Breaks down completely in water and gives off many H+ ions
• Weak acid


  Only partially breaks down, gives off much less H+ than a strong acid
• Characteristics of an Acid

  • Sour taste
  • React to metals and carbonates to produce gas
  • Contain hydrogen
• Properties of an Acid

  • Conducts electricity
  • Corrosive: they break down certain substances
  • Many acids can corrode fabric, skin and react strongly with metals
  • Turns blue litmus paper to red
• Base


  A solution that has an excess of OH- ions, also known as alkali
• Properties of a Base

  • Feels slippery
  • Tastes bitter
  • Corrosive
  • Does not react to metals
  • Turns red litmus paper into blue
• Acid-Base Strength


  • A concentrated strong acid has a low pH value
  • A concentrated strong base has a high pH value
  • pH stands for "potential hydrogen" and is a measure of how many H+ ions there are in a solution
  • The more H+ there are, the fewer the pH will be
• pH


  • Measure of how acidic or basic a solution is
  • The pH scale ranges from 0-14, a solution with a pH of 7 is neutral
  • Basic solutions have a pH that values above 7, acids have a pH from 0-7, lower pH value indicates a stronger acid
• Measuring pH


  Using special strips of paper called pH paper
• Factors Affecting Solubility


  • Effect of stirring (increases chances of contact)
  • Effect of particle size (smaller particles have more edges and corners where the solvent can be in contact)
  • Nature of solute and solvent (like dissolves like, polar and ionic substances are soluble in polar solvents, non-polar substances are soluble in non-polar solvents)
  • Temperature (solubility of most solids in water increases with temperature)
  • Pressure (gas solubility in liquid is directly proportional to the pressure of that gas above the surface of solution)
• Effervescence


  Rapid escape of gas from the liquid
• Henry's Law


  States that at a given temperature, the solubility of gas in liquid is directly proportional to the partial pressure of the gas above the liquid
• Pure Substance


  • Form of matter that has a constant composition and properties that are constant throughout the sample
  • Elements and compounds are both examples of pure substances
• Melting Point


  Point at which materials changes from solid to liquid
• Boiling Point


  Temperature point at which the material transforms into the gas phase in the liquid phase
• Solubility of Solute


  The property of solute to dissolve in a solvent
• Solubility


  Defined as the number of grams of solute that dissolves in 100g of a solvent to form a saturated solution at a given temperature and pressure
• Saturated Solution


  Solution that contains the maximum amount of solute dissolved in a given solvent, no more solute dissolves
• Unsaturated Solution


  Contains less dissolved solute than a saturated solution, more solute dissolves