Overview
This lecture covers foundational chemistry concepts, focusing on periodic table organization, chemical bonding, atomic structure, unit conversions, nomenclature, stoichiometry, and types of chemical reactions.
The Periodic Table & Element Properties
- Elements are organized into groups (columns) and periods (rows) based on similar properties.
- Group 1A: Alkali metals (highly reactive, 1 valence electron, form +1 ions).
- Group 2A: Alkaline earth metals (reactive, 2 valence electrons, form +2 ions).
- Transition metals (groups 3-12) often have variable charges; some, like zinc, primarily have +2.
- Groups 13-18: Representative elements, including nonmetals, metalloids, and halogens.
- Halogens (group 17/7A): Very reactive nonmetals, form -1 ions.
- Noble gases (group 18/8A): Chemically inert, stable electron configurations.
- Metals are left/below the “staircase” line; nonmetals are above/right; metalloids border the line.
Chemical Bonding & Molecules
- Ionic bonds involve electron transfer between metals and nonmetals.
- Covalent bonds involve sharing electrons between nonmetals; sharing can be equal (non-polar) or unequal (polar).
- Diatomic elements (exist naturally as molecules): H₂, N₂, O₂, F₂, Cl₂, Br₂, I₂.
Atomic Structure & Isotopes
- Atomic number = number of protons; mass number = protons + neutrons.
- Valence electrons are in the outermost energy level; core electrons are inner.
- Isotopes: Same atomic number, different mass numbers (different neutrons).
- Average atomic mass is a weighted average of all isotopes.
Classification of Substances & Mixtures
- Pure substances: only one type of element or compound.
- Compounds can be molecular (covalent) or ionic.
- Mixtures: combination of two or more pure substances (homogeneous if uniform, heterogeneous if not).
Unit Conversions & Metric System
- Standard conversion factors (e.g., 1 km = 1000 m, 1 in = 2.54 cm).
- Metric prefixes: kilo (10³), centi (10⁻²), milli (10⁻³), micro (10⁻⁶), nano (10⁻⁹).
- Use dimensional analysis for unit conversions, adjusting for area and volume as needed.
Significant Figures & Calculations
- Nonzero digits and zeros between them are significant.
- Leading zeros are not significant; trailing zeros are significant if there’s a decimal.
- For multiplication/division, round to the least number of sig figs; for addition/subtraction, round to the least decimal places.
Nomenclature of Compounds
- Use prefixes (mono-, di-, tri-, etc.) for naming molecular compounds.
- Ionic compounds: name cation, then anion (add -ide for monatomic anions).
- Polyatomic ion nomenclature: memorize common ions (e.g., sulfate, nitrate, ammonium).
Acids & Naming
- Acids containing -ate ions become -ic acids (e.g., sulfate → sulfuric acid).
- -ite ions become -ous acids; -ide ions use the prefix “hydro-” and suffix “-ic.”
Stoichiometry: Moles, Mass, and Atoms
- 1 mole = 6.02 × 10²³ particles (Avogadro’s number).
- Molar mass: grams per mole (from periodic table).
- Mass percent = (mass of element / total mass) × 100%.
- Convert between grams, moles, atoms, and molecules using molar mass and Avogadro’s number.
Chemical Reactions & Balancing
- Types: combustion, combination (synthesis), decomposition, single replacement, double replacement (including precipitation and acid-base).
- Balance equations by adjusting coefficients, not subscripts.
- Redox (oxidation-reduction) reactions transfer electrons; recognize redox by changes in oxidation states or presence of pure elements.
- Write net ionic equations by removing spectator ions.
Key Terms & Definitions
- Valence electrons — electrons in the outermost shell of an atom.
- Isotope — atoms of the same element with different numbers of neutrons.
- Mole — amount containing 6.02 × 10²³ particles.
- Ionic bond — attraction between oppositely charged ions (metal + nonmetal).
- Covalent bond — sharing of electrons between two nonmetals.
- Anion — negatively charged ion.
- Cation — positively charged ion.
- Molar mass — mass (g) of 1 mole of substance.
- Oxidation state — charge an atom would have if electrons were transferred completely.
Action Items / Next Steps
- Memorize common element names, charges, and polyatomic ions.
- Practice unit conversions and significant figure rules.
- Review and practice naming compounds, acids, and writing chemical formulas.
- Balance chemical equations and identify reaction types.
- Complete assigned textbook readings and relevant end-of-chapter problems.