How to write, name and/or draw various Chemical Compounds Bonds and Compounds How to write, name and/or draw various Chemical Compounds

Ions and Ionic Compounds An ion is created whenever an atom gains or loses an electron to become more stable like a Noble Gas, meaning that its valence number is now 8! Metals are always positive, which means that they lose electrons. Nonmetals are usually negative with a few exceptions, like Nitrogen which has 8 different ion possibilities.

How to make an ionic compound To make an ionic compound, one must combine a positive ion with a negative ion. The positive ion is ALWAYS listed first, followed by the negative one. Example: Na+ + Cl-  NaCl **The Key is that ALL charges must be cancelled out, and the overall charge on the compound MUST be ZERO!!

Criss-Cross Method When the ratio is one-to-one or two-to-two, it is easy to cancel the charges. However, it can become a little more complicated, so scientists use the Criss-Cross Method to help illustrate how the math is done. Example: Fe3+ + SO42- = Fe2(SO4)3

Naming Ionic Compounds The first part of the name comes directly from the first ion in the compound. The second part of the name has the base of the second ion, but MUST end in –ide, -ate, or –ite. Examples: NaCl Sodium Chloride K2CrO4 Potassium Chromate Al2(SO3)3 Aluminum Sulfite

Writing the formula from the name Unfortunately, there is no shortcut to this. You MUST learn the ion to know what their charges are to write the formula from the names. It takes practice and perseverance. Examples: Calcium Carbonate CaCO3 Ammonium Phosphate (NH4)3PO4

Review and Practice Name the following ionic compounds: (NH4)3PO4 CaSO4 Write the formulas for the following ionic compounds: Tin (IV) Fluoride Iron (III) peroxide

More Practice Write the formulas for the following ionic compounds: Magnesium Hydroxide Copper (I) Sulfate Lead (II) Phosphate Ammonium Dichromate Zinc Acetate Iron (II) Oxide Mercury (I) Chloride Silver Nitrate

Covalent or Molecular Compounds Covalent compounds are created using covalent bonds. A covalent bond involves the “sharing’ of electrons between two different atoms. These atoms can be the same type of atoms or different. To show the sharing of electrons, scientists use Lewis Dot Structures and structural formulas that use dashes for bonds.

Naming Covalent Compounds Number Prefix 1 Mono- 2 Di- 3 Tri- 4 Tetra- 5 Penta- 6 Hexa- 7 Hepta- 8 Octa- 9 Nona- 10 Deca- To name covalent compounds, one must know ten important prefixes. These prefixes indicate how many of each atom is present in the molecule that has been created.

Naming them… First, you must see if the two atoms are nonmetals. If so, then you have a covalent compound. (Be careful not to mistake an ion for an atom!) Second, note how many of each atom is present in the compound. Third, choose the prefix that will work for the name. (The first atom only gets a prefix if there is more than one; the second atom ALWAYS gets a prefix.) Fourth, name it using the prefixes as needed. (Be careful…some compounds have common names that are the preferred names.

Examples… CO2 Carbon dioxide H2O Dihydrogen monoxide (Water) NH3 Nitrogen trihydride (Ammonia) P4O10 Tetraphosphorus decoxide

Types of Chemical Reactions There are five major types of reactions. These reactions are found in nature and can be manmade. In addition, these reactions often take in heat or energy (endothermic) or release heat or energy (exothermic).

Synthesis Reactions These reactions have two or more reactants that come together to form ONE product. Generic equation: A + B  AB Example: 2H2 + O2  2H2O

Decomposition Reactions These reactions involve ONE reactant breaking down to form two or more products. Generic Equation: AB  A + B Example: RhO3  RhO + O2

Single-Replacement Reactions These reactions require a single atom combined with a compound to then form a new compound and a new singular atom. (**Governed by the Activity Series of Metals) Generic Equation: A + BC  AC + B Example: 2Li + H2SO4  Li2SO4 + H2

Double-Replacement Reactions These reactions involved two ionic compounds’ cations switching anion partners to form new compounds. (**A gas or precipitate usually forms!) Generic Equation: A+B- + C+D-  A+D- + C+B- Example: AgBr + NaCl  AgCl + NaBr

Combustion Reactions All combustion reactions involve oxygen gas as a reactant and the release of great amounts of energy as a product. There are types of combustion reactions: Metals with oxygen to form metal oxides and hydrocarbons with oxygen to form carbon dioxide and water.

Combustion Reactions (cont.) Examples of both combustion reactions: 2Mg + O2  2MgO + light C2H4 + 3O2  2CO2 + 2H2O + energy