Unit 1 chem

• What do scientists use to summarize changes in reactions?

  Formulae and equations
• What are some important ions to remember for writing chemical formulae?

  • Nitrate: NO₃⁻
  • Carbonate: CO₃²⁻
  • Sulfate: SO₄²⁻
  • Hydroxide: OH⁻
  • Ammonium: NH₄⁺
  • Phosphate: PO₄³⁻
  • Silver: Ag⁺
• How can you deduce the formula of an ionic compound?

  Using the formulae and charges of the ions
• What is the formula of calcium nitrate?

  Ca(NO₃)₂
• When are brackets used in chemical formulae?

  When there is more than one type of ion
• How do you determine the number of bonds an atom will form in a covalent molecule?

  By calculating 8 minus its group number
• What is the formula for carbon dioxide?


  CO₂
• What is the balanced equation for the reaction of ethanol with oxygen?

  C₂H₅OH + 3O₂ → 2CO₂ + 3H₂O
• How can you predict the charge on some ions based on their periodic table position?

  By following simple rules for groups
• What charge do metals in groups 1, 2, and 3 typically form?

  1+, 2+, and 3+ ions
• What charge do non-metals in groups 5, 6, and 7 typically form?

  3–, 2–, and 1– ions
• Why must the numbers of each atom balance in a chemical equation?

  Atoms cannot be created or destroyed
• What is the balanced equation for the combustion of methane?

  CH₄ + 2O₂ → CO₂ + 2H₂O
• What do the large numbers before a formula in a chemical equation indicate?

  How many molecules participate in the reaction
• How do you balance the equation Na₂CO₃ + HCl → NaCl + CO₂ + H₂O?

  Na₂CO₃ + 2HCl → 2NaCl + CO₂ + H₂O
• What state symbols represent solid, liquid, and gas?

  (s), (l), and (g)
• What does Bohr's model describe about electrons in atoms?

  The shapes in space where electrons can be found
• How many electrons can the first four shells hold?

  2, 8, 18, and 32
• What is the atomic number of an atom equal to?

  The number of protons in an atom
• What are atomic orbitals?

  Regions in space where electrons may be found
• What are the first four types of orbitals?

  s, p, d, and f orbitals
• What is the Aufbau principle?

  Electrons fill lower shells before higher shells
• How are paired electrons represented in diagrams?

  As arrows pointing in opposite directions
• What is the relationship between bond length and bond strength in covalent bonds?

  Shorter bond length means greater bond strength
• What is metallic bonding?

  Attraction between positive ions and delocalised electrons
• What are the key properties of metals due to metallic bonding?

  • Electrical and thermal conductivity
  • High melting and boiling points
  • Malleability
  • Ductility
• What is the structure of metallic bonding?

  A giant lattice of positive ions
• How does the size of metal atoms affect melting points?

  Larger atoms have lower melting points
• Why do group 2 metals have higher melting points than group 1 metals?

  Group 2 metals have two delocalised electrons
• What are intermolecular forces?

  Interactions between molecules caused by dipoles
• What are London forces also known as?

  Van der Waals forces
• What causes permanent dipoles in polar molecules?

  Differences in electronegativity between atoms
• What is a temporary dipole?

  An uneven distribution of electrons in a molecule
• What is the result of a temporary dipole in a nearby molecule?

  It induces a temporary dipole
• What are the types of intermolecular forces?

  • London forces
  • Dipole-dipole interactions
• What do electron configuration diagrams represent?

  The arrangement of electrons in atoms or ions
• What do dot and cross diagrams show?

  The bonding between atoms using dots and crosses
• What is a lone pair in covalent bonding?

  Non-bonded electrons on an atom
• What shape does methane form due to its bonding?

  Tetrahedral shape
• How does the charge/size ratio affect ionic bond strength?

  Higher charge and smaller size increase strength