Overview
This lecture introduces fundamental chemistry concepts, focusing on the periodic table, types of elements and compounds, naming conventions, and calculating atomic structure details.
The Periodic Table & Element Groups
- The periodic table organizes elements by atomic number and chemical properties.
- Group 1 (alkali metals): Li, Na, K, Rb, Cs, form +1 ions, except H.
- Group 2 (alkaline earth metals): Be, Mg, Ca, Sr, Ba, form +2 ions.
- Groups 13–18 offer varied charges; e.g., Group 13 (3A) forms +3, Group 14 (4A) can form +2 or +4.
- Group 15 (5A): N, P form -3 ions; Group 16 (6A, chalcogens): O, S, Se form -2 ions.
- Group 17 (7A, halogens): F, Cl, Br, I form -1 ions; highly reactive.
- Group 18 (8A, noble gases): He, Ne, Ar, etc., are chemically inert.
- Groups 3–12 are transition metals, often with variable charges.
Atoms, Molecules, Elements, and Compounds
- Atoms: single particles of an element (e.g., Fe, Zn).
- Molecules: two or more atoms bonded (e.g., H₂, O₂, S₈, Cl₂).
- Pure element: substance with only one type of atom (can be atomic or molecular).
- Compound: substance with different types of atoms, may be ionic (NaCl) or molecular (CO₂).
Metals, Nonmetals, and Metalloids
- Metals (left of staircase line): conductors, form cations.
- Nonmetals (right of line): insulators, form anions.
- Metalloids (along line): intermediate properties (e.g., B, Si, Ge, As).
Naming Compounds
- Molecular: use prefixes (mono-, di-, tri-, etc.); e.g., CO₂ is carbon dioxide.
- Ionic: name cation (+) then anion (add "-ide"); do not use prefixes, e.g., NaCl is sodium chloride.
- Transition metals with variable charge use Roman numerals (e.g., FeCl₂ is iron(II) chloride).
Polyatomic Ions
- Common examples: sulfate (SO₄²⁻), hydroxide (OH⁻), ammonium (NH₄⁺), nitrate (NO₃⁻), phosphate (PO₄³⁻).
- Memorize their formulas and charges for naming compounds.
Writing Formulas
- For molecular compounds: use element symbols and prefixes.
- For ionic compounds: balance total positive and negative charges; use subscripts as needed.
- For polyatomic ions: use parentheses when more than one is present.
Isotopes & Atomic Structure
- Isotopes: atoms of the same element with different numbers of neutrons.
- Number of protons = atomic number.
- Number of neutrons = mass number - atomic number.
- Number of electrons = atomic number minus charge (for ions).
Key Terms & Definitions
- Valence Electron — outermost electron involved in bonding.
- Ion — charged particle formed when atoms gain/lose electrons.
- Cation — positively charged ion.
- Anion — negatively charged ion.
- Isotope — atom of same element with different numbers of neutrons.
- Polyatomic Ion — ion composed of multiple atoms bonded together.
Action Items / Next Steps
- Print and study a periodic table.
- Memorize element names, common polyatomic ions, and naming rules.
- Practice writing names and formulas of compounds.
- Complete any quiz or homework assigned on element and compound classification.