Rev#1_Chemistry Pt. 2

• Electronegativity


  The attraction of an atom for shared electrons
• Metals react with oxygen gas


  Forming a basic oxide in water
• Nonmetals react with oxygen gas


  Forming an acidic oxide in water
• Chemical symbol


  An element is represented by a symbol which may be one or two letters; the first is capitalized and the second is in the lower case. The symbols may be derived from the Greek, German or Latin names of the elements.
• Binary covalent compounds


  Formed between two non-metals
• Naming binary covalent compounds

  1. Identify the elements present in the compound given by the chemical formula. The name of the more metallic element is written first.

  2. Change the suffix of the less metallic element to -ide.

  3. Use the prefix corresponding to the number of atoms present in the compound.
• Prefixes for number of atoms

  • Mono-
  • Di-
  • Tri-
  • Tetra-
  • Penta
  • Hexa-
  • Hepta-
  • Octa-
  • Nona-
  • Deca-
• The mono- prefix is frequently omitted, particularly for well-known substances. If no prefix is use, it usually implies that no number of atoms of element is one. However, experts in nomenclature caution that this can be dangerous and suggest that it is better to include the mono- prefix.
• Some compounds are known only by their common names.
• Writing formulas of binary compounds

  1. Represent each kind of element in a compound with the correct symbol of element.

  2. Indicate by a subscript the number of atoms of each element in a molecule of the compound.

  3. Write the symbol of the more metallic element first. (H is an exception to this rule.)
• Ionic compounds


  Compounds formed between metals and nonmetals
• Naming ionic compounds


  1. Write the name of the cation first, followed by the name of the anion.

  2. Unlike binary covalent compounds, PREFIXES ARE NOT USE to indicate the number of ions present in the formula.

  3. Most transition metals can exist in more than one ionic form. Thus, it is important to know the charge of the cations in their compounds.
• Ionic compound naming systems

  • Stock system
  • Old system
• Hydrates


  Ionic compounds that contain a certain proportion of water molecules apart from the ions of the compound
• Writing formulas of ionic compounds

  1. Write the symbol of the positive ion (cation) first, followed by the symbol of the negative ion (anion).

  2. Write the charge of each ion over the symbol of that ion. Usually, for the main group elements, the group number usually gives the charge of the monoatomic ion.

  3. Choose a subscript that will make the net charge zero. The simplest procedure is to use the absolute value of the charge of the anion as the subscript for the cation; and the absolute value of the cation charge as the subscript for the anion (CROSS-OVER RULE).

  4. For hydrates, follow the same steps, then add a centered dot, followed by the number of water molecules (indicated by the prefix) and the chemical formula of water.
• Binary acids


  Contain only two different elements- hydrogen and a nonmetal
• Naming binary acids


  Binary acids are named as hydro _ ic acid, where the stem of the nonmetal is inserted in place of the line.
• Oxyacids


  Acids derived from the oxyanions
• Naming oxyacids


  1. If the name of the oxyanion ends in -ate, the name of the oxyacid will be of the form ic acid.

  2. If the name of the oxyanion ends in -ite, the name of the oxyacid will be of the form ous acid.
• Names and Symbols of Some Common Polyatomic Anions

  • Hydroxide (OH-)
  • Peroxide (O2^2-)
  • Cyanide (CN-)
  • Azide (N3-)
  • Nitrate (NO3-)
  • Nitrite (NO2-)
  • Acetate (CH3COO-)
  • Chromate (CrO4^2-)
  • Sulfate (SO4^2-)
  • Dichromate (Cr2O7^2-)
  • Sulfite (SO3^2-)
  • Permanganate (MnO4-)
  • Bisulfate (HSO4-)
  • Oxalate (C2O4^2-)
  • Bisulfite (HSO3-)
  • Phosphate (PO4^3-)
  • Hydrogen phosphate (HPO4^2-)
  • Dihydrogen phosphate (H2PO4-)
  • Thiocyanate (SCN-)
  • Carbonate (CO3^2-)
  • Hydrogen carbonate or bicarbonate (HCO3-)
• Chemical reactions


  Processes in which substances are changed into one or more new substances
• Chemical equation


  Represents a chemical reaction, with reactants on the left and products on the right
• Chemical reactions follow the law of conservation of mass
• Balancing chemical equations


  1. Use correct chemical formulas

  2. Adjust only the coefficients, NOT the subscripts

  3. Balance elemental forms (e.g. Ar, Cu, Na, O2, N2, 12, Sa...) and H and O last.

  4. Use the simplest possible set of whole no. coefficients
• Stoichiometry


  The quantitative study of reactants and products in a chemical reaction
• Mole method for stoichiometry

  1. Write correct chemical formulas and balance the equation.

  2. Convert the quantities into moles.

  3. Use the mole ratios to calculate moles of the required substance.

  4. Convert calculated moles to whatever units required.
• Three types of stoichiometry calculations

  • Moles reactant to moles product
  • Mass reactant to moles reactant
  • Moles reactant to mass product
• Mole


  The amount of substance that contains the same number of elementary particles as the number of atoms in exactly 12 grams of C-12
• Expressing the mole


  1. By number of particles (use Avogrado's number, 6.02 x 10^23 particles per mole)

  2. By mass (use molar mass)

  3. By volume (use molar volume, 22.4 L at STP)
• Interconverting moles, mass, and number of particles

  1. Mass = Moles x Molar Mass

  2. Number of particles = Moles x 6.02 x 10^23
• Molar mass


  The mass in grams of 1 mole of a substance. Numerically equal to the atomic mass (or atomic weight) of an atom or the formula mass of a molecule, a compound or a polyatomic ion.
• Percentage composition


  A list of the percentages by weight of the elements in a compound
• Empirical formula


  The formula with lowest possible whole number subscripts to represent the composition of the compound
• Molecular formula


  Gives the actual composition or the actual number of atoms of each element present in one molecule or one formula unit of the compound
• Chemical stoichiometry


  The quantitative relationship of the amounts of reactants used and amounts of products formed in a reaction
• Percent yield


  The portion of the theoretical yield of product that is actually obtained in the reaction
• Theoretical yield


  The amount of product that would result if all the limiting reactant reacted
• Actual yield


  The amount of product actually obtained from a reaction
• Limiting reactant


  The reactant that is completely consumed in the reaction, determining the amount of products that can be formed
• Excess reactant


  The reactant that is not completely used up in a chemical reaction