chem 2/18

Phase Two Review of Ionic Compounds

Halogens

• Typically have a -1 charge, meaning they tend to gain one electron to achieve a stable electron configuration.

• Examples include:

  • Fluorine (F): the most electronegative element, and is highly reactive, often forming fluoride ions (F-).

  • Chlorine (Cl): also very reactive, commonly used in disinfection and forms chloride ions (Cl-).

  • Bromine (Br): exists as a liquid at room temperature and forms bromide ions (Br-).

  • Iodine (I): a solid at room temperature, it forms iodide ions (I-) and is essential for thyroid function in humans.

• Halogens are known for their high reactivity and exist naturally as diatomic molecules (e.g., Cl2, F2, Br2, I2), meaning two atoms bond together to form a molecule.

Oxygen Group Elements

• Elements such as:

  • Oxygen (O): vital for life; it typically forms oxides (e.g., H2O) with metals and is crucial in respiration.

  • Sulfur (S): often found in ores and used in the production of sulfuric acid (H2SO4) and sulfides (e.g., ZnS).

  • Selenium (Se): used in photocopiers and found in some enzymes, can form selenides.

• Tend to have a -2 charge by gaining two electrons. These elements play a crucial role in forming compounds with both metals and nonmetals. For instance, oxygen forms oxides with many metals, crucial for creating various industrial compounds.

Transition Metals

• Notable compounds with transition metals include:

  • H3O+ (Hydronium): indicates the presence of water molecules, important in acid-base chemistry.

  • OH- (Hydroxide): fundamental in base chemistry and plays a major role in pH balance.

  • O2- (Oxide): an anion critical for various reactions in inorganic chemistry.

  • CN- (Cyanide): highly toxic; used in electroplating and mining.

  • N3- (Azide): known for its explosive properties and used in propellants.

  • CO3^2- (Carbonate): important in geological and biological systems.

  • NO3- (Nitrate): used in fertilizers, crucial for plant growth.

  • NO2- (Nitrite): can form in soil, also used in food preservation.

  • SO4^2- (Sulfate): widely used in industrial applications, including detergents.

  • PO4^3- (Phosphate): essential for life, used in DNA and ATP, and in fertilizers.

• Transition metals can hold various oxidation states (e.g., +1, +2, +3), which contributes to their versatility in chemical reactions, allowing them to form many complex ions and coordination compounds.

Balancing Charges

• To achieve electrical neutrality, use common multiples to find charge balance in ionic compounds.

• Example: In Copper(I) oxide (Cu2O), the +1 charge from copper requires a -2 charge overall, necessitating the use of 2 Cu+ ions to balance the charge. Thus, the total charge in the compound becomes zero. Understanding charge balancing is vital for predicting the proportions in which elements will combine.

Naming Ionic Compounds

• When identifying the names and formulas of ionic compounds:

  • Example: Chromium(III) Phosphide (CrP) indicates that chromium can form more than one type of ion, reflected by the Roman numeral III, which shows the +3 charge of chromium.

  • Example: Mercury(II) Sulfide (HgS) shows the +2 charge of mercury, essential in distinguishing compounds made with different ionic forms of the same element.

• The name of the compound reflects the elements' charges, allowing chemists to understand how the compound will behave in reactions.

Molecular Compounds Naming

• Typically involve nonmetals:

  • Utilize a prefix for the first element (if there is more than one) and a prefix for the second element followed by an -ide suffix to indicate that it is a molecular compound.

  • Example: Dinitrogen Trioxide (N2O3) indicates the presence of two nitrogen atoms and three oxygen atoms, showing how prefixes are used (di- for two, tri- for three).

Acids Naming

• Discuss acid naming conventions that will be covered in later chapters.

• Common examples include hydrochloric acid (HCl) for a strong acid, which completely dissociates in water, and acetic acid (CH3COOH) for a weak acid, which partially dissociates, indicating its role in organic chemistry and daily life.