Overview
This lecture covers fundamental topics in introductory chemistry, focusing on the periodic table, chemical bonding, unit conversions, naming compounds, stoichiometry, reaction types, and significant figures.
Periodic Table & Element Classification
- Group 1A: Alkali metals (except hydrogen) are highly reactive and form +1 ions.
- Group 2A: Alkaline earth metals are reactive, form +2 ions, and have two valence electrons.
- Transition metals (groups 3–12): often have variable charges; some have common states (e.g., Zn²⁺).
- Groups 13–18: Representative elements; Group 17 are halogens (most reactive nonmetals), Group 18 are inert noble gases.
- Metals (conductors), nonmetals (insulators), and metalloids (semiconductors) are located in specific periodic table regions.
- Seven diatomic elements: H₂, N₂, O₂, F₂, Cl₂, Br₂, I₂.
Atomic Structure & Isotopes
- Atomic number = number of protons; mass number = protons + neutrons.
- Valence electrons are outermost electrons; core electrons are all others.
- Isotopes are atoms of the same element with different numbers of neutrons.
Chemical Bonding
- Ionic bonds: transfer of electrons, formed between metals and nonmetals.
- Covalent bonds: sharing of electrons, usually between nonmetals; can be polar (unequal sharing) or non-polar (equal sharing).
- Polyatomic ions contain multiple atoms bonded covalently but carry a charge.
Compounds, Mixtures, and Classification
- Pure substances: elements or compounds; mixtures are combinations of pure substances.
- Homogeneous mixtures: uniform composition (e.g., air); heterogeneous: visibly distinct phases (e.g., oil & water).
- Molecular compounds: nonmetal + nonmetal; ionic compounds: metal + nonmetal.
Naming Compounds
- Use prefixes (mono-, di-, tri-, etc.) for covalent (molecular) compounds.
- For ionic compounds, use cation + anion (add -ide to the anion); use Roman numerals for metals with variable charge.
- Learn common polyatomic ions (sulfate, nitrate, phosphate, etc.).
Acid Nomenclature
- -ate → -ic acid; -ite → -ous acid; -ide → hydro-…-ic acid.
- Add H atoms to balance the charge for acid formulas.
Key Terms & Definitions
- Valence electron — outermost electron involved in bonding.
- Isotope — atoms of same element, different neutrons.
- Cation/Anion — positive/negative ions.
Action Items / Next Steps
- Memorize names, symbols, and charges for common elements and polyatomic ions.
- Practice unit conversion problems and significant figures.
- Review the rules for naming compounds and acids.
- Balance reaction equations and write net ionic equations.
- Prepare for quizzes on element names, periodic table groups, and compound classification.