CHEM2

• What is an element?

  A particle made up of 1 type of atom that cannot be made chemically simpler.
• What is a compound?

  A particle made up of 2 or more elements that are chemically bonded together in a fixed ratio.
• What is a mixture?

  Something made up of different compounds and elements.
• What happens when two elements react?

  They form a compound with different properties than the elements.
• What is the observation when sodium reacts with water?

  There is lots of effervescence.
• How does sodium chloride behave when it comes in contact with water?

  There is no effervescence.
• How do you name a compound with oxygen?

  It should end in –ate, except for hydrogen which becomes hydroxide.
• What is the name of the compound CuO?

  Copper Oxide
• What is the name of the compound CaCO3?

  Calcium Carbonate
• What is the name of the compound CuS?

  Copper Sulphide
• What is the name of H2O?

  Dihydrogen Oxide
• What is the formula for Sulfuric Acid?

  H2SO4
• What is the formula for Nitric Acid?

  HNO3
• What is the formula for Phosphoric Acid?

  H3PO4
• What is the formula for Hydrochloric Acid?

  HCl
• What is a solute?

  The substance you dissolve in a solvent.
• What is a solvent?

  The liquid you dissolve the solute in.
• What is a solution?

  The end result after you put the solute in the solvent.
• How does filtration work?

  It separates mixtures made of an insoluble solid and a liquid.
• What happens during evaporation?

  The liquid evaporates, leaving the soluble solid behind.
• What is simple distillation used for?

  To separate two liquids with different boiling points.
• How does chromatography work?

  It separates different colors by their solubility.
• What is the approximate radius of an atom?

  About 0.1 μm (1 ∗ 10^{-10} m).
• What is the radius of the nucleus compared to the atom?

  Less than 1/10000 of the atom (about 1 ∗ 10^{-15} m).
• What does the periodic table show about an element?

  The number of protons, neutrons, and electrons.

  
• What is an isotope?

  Atoms of the same element with different numbers of neutrons.
• Why do some elements have decimal numbers for their mass number on the periodic table?

  Because they have different isotopes.
• What does the mass number of an element represent?

  The relative atomic mass of an element.
• What is relative atomic mass (Ar)?

  An average value that takes into account the abundance of isotopes.
• What is the formula for calculating relative atomic mass?

  $A_r =$$\frac{\text{sum of (isotope abundance} \times \text{mass number)}}{\text{Total abundance}}$
• Calculate the relative atomic mass of chlorine given the following abundances: 35 Cl has 75% and 37 Cl has 25%.

  $A_r =$ \frac{(75 \times 35) + (25 \times 37)}{100} =$35.5$
• What are the rules for electron configuration?

  Electrons fill from the closest shell to the nucleus outwards.
• How many electrons can fill the first shell?

  A maximum of 2 electrons.
• How many electrons can fill the second shell?

  A maximum of 8 electrons.
• How are electrons represented in diagrams?

  As crosses.
• What does the period of an element indicate?

  How many shells there are.
• What does the group number of an element indicate?

  How many electrons are on the last shell.
• What is an ion?

  A charged particle formed when an atom loses or gains electrons.
• What happens when an atom loses electrons?

  It becomes a positively charged ion.
• What happens when an atom gains electrons?

  It becomes a negatively charged ion.