Overview
This lecture covers predicting ionic charges based on the periodic table, naming ionic compounds, and using Roman numerals for transition metal complexes.
Predicting Ionic Charges
- Group 1A elements form ions with a +1 charge.
- Group 2A elements form ions with a +2 charge.
- Group 3A elements form ions with a +3 charge.
- Group 7A elements form ions with a -1 charge.
- Group 6A elements form ions with a -2 charge.
- Group 5A elements form ions with a -3 charge.
- Group 6A peroxides are an exception with a -1 charge.
- Group 4A elements generally form molecular compounds, not typical ions.
Naming Transition Metal Compounds
- Transition metals require a Roman numeral to show their cation charge in compound names.
- The Roman numeral indicates the oxidation state of the metal.
- Example: CuO is copper (II) oxide; copper has a +2 charge here.
- Example: Cu2O is copper (I) oxide; copper has a +1 charge here.
Writing and Naming Binary Ionic Compounds
- The charge of the ions determines the chemical formula so charges balance to zero.
- Example: Iron (III) bromide means Fe has a +3 charge, Br is -1, so formula is FeBr3.
- Example: Titanium (IV) sulfide means Ti is +4, S is -2, so formula is TiS2.
- The thought process starts by identifying ion charges and ensuring the overall compound is neutral.
Key Terms & Definitions
- Ionic charge — The electric charge an atom gains or loses when forming an ion.
- Transition metal — Elements in the middle of the periodic table that often have variable oxidation states.
- Roman numeral — Number in parentheses in compound names showing the charge of a transition metal cation.
- Binary compound — A compound composed of two different elements.
Action Items / Next Steps
- Practice predicting ionic charges for different groups.
- Try writing and naming formulas for transition metal compounds using Roman numerals.