Overview
This lecture covers the structure of the periodic table, key element groups, chemical properties, trends, important element symbols, and ion formation.
Structure of the Periodic Table
- Columns in the periodic table are called groups; rows are called periods.
- Elements in the same group share similar chemical properties.
- Groups are numbered 1–18 (or 1A–8A in some naming systems).
- Periods are the horizontal rows; lanthanides and actinides are placed below the table.
Major Element Groups and Properties
- Group 1: Alkali metals (e.g., Li, Na, K) are very reactive, low density, low melting points, and form +1 ions.
- Group 2: Alkaline earth metals (e.g., Mg, Ca) are reactive (less than Group 1) and form +2 ions.
- Groups 3–12: Transition metals have multiple possible ion charges (oxidation states).
- Group 16: Chalcogens (e.g., O, S) form -2 ions.
- Group 17: Halogens (e.g., F, Cl) are non-metals, form -1 ions, and are very reactive.
- Group 18: Noble gases (e.g., He, Ne, Ar) are inert and chemically nonreactive.
Valence Electrons and Ion Formation
- Group number indicates number of valence electrons (except He, which has 2).
- Metals (left side): Conduct electricity, malleable, ductile, form positive ions (cations).
- Non-metals (right side): Poor conductors, brittle, form negative ions (anions).
- Metalloids (borderline elements): Show properties of both metals and non-metals; are semiconductors.
Atomic Structure and Isotopes
- Element symbol: One or two-letter abbreviation (e.g., H for hydrogen).
- Atomic number (top number): Number of protons, identifies the element.
- Atomic mass (bottom number): Weighted average of isotopes (not necessarily a whole number).
- Isotopes: Atoms of same element with different neutrons (e.g., carbon-12, carbon-13, carbon-14).
Common Elements and Their Uses
- H (hydrogen): Fuel in stars.
- He (helium): Balloons.
- Li (lithium): Batteries.
- Na (sodium): Table salt (NaCl).
- K (potassium): Found in bananas.
- Fe (iron): Essential metal.
- Cu (copper), Ag (silver), Au (gold): Electrical wiring, wealth storage.
- C (carbon): Forms include graphite, diamond, and carbon dioxide.
- O (oxygen): Air, diatomic molecule.
- N (nitrogen): Major air component, diatomic molecule.
- F (fluorine): Toothpaste.
- Cl (chlorine): Disinfectant.
- Ne (neon): Neon lights.
- Ar (argon): Found in air.
- Pb (lead): Batteries.
Key Terms & Definitions
- Group — Vertical column in the periodic table.
- Period — Horizontal row in the periodic table.
- Valence electrons — Electrons in the outermost shell.
- Cation — Positively charged ion (formed by metals).
- Anion — Negatively charged ion (formed by non-metals).
- Isotope — Atoms of the same element with different numbers of neutrons.
- Allotropes — Different structural forms of the same element.
Action Items / Next Steps
- Memorize element symbols and names for common elements.
- Review group properties and typical ion charges.
- Study the location and characteristics of metals, non-metals, and metalloids.