Overview
The lecture discussed the basic concepts of mass, mole, and classifications of elements, molecules, and compounds, using the periodic table as a basis.
Mass and Mole
- Mass refers to weight.
- Mole refers to the number of particles.
- Atomic mass — weight of an atom, measured in AMU (atomic mass unit).
- Molar mass — weight of one mole of a substance, measured in grams/mole.
- Molecular mass and molar mass are the same, meaning the total weight of a group of atoms or molecules.
- Formula mass — weight of the formula unit of an ionic compound like NaCl.
Classification of Substances
- Element — composed of one type of atom (e.g., S8, N2).
- Compound — has two or more types of atoms (e.g., H2O, NH3).
- Molecule — group of two or more atoms, which may be the same or different types.
- Not all molecules are compounds, and not all elements are molecules.
- Diatomic elements — molecules that always have two atoms (e.g., O2, N2, H2, Cl2, F2, Br2, I2).
Periodic Table and Groups
- Alkali metals: Group 1 (Halina kay Ruby Si Friday Na).
- Alkaline earth metals: Group 2 (Be-Mag-Dusa-Ka-Senora-Barbara).
- Transition metals — variable charges, no need to memorize.
- Icosagens — proper name for the boron group (Group 3).
- Crystallogens — name for the carbon group (Group 4); carbon and silicon both form crystals.
- Halogens — F, Cl, Br, I; most reactive.
- Noble gases — inert or non-reactive.
- The color in the periodic table indicates if the element is a gas (red) or liquid (blue).
Carbon and Allotropes
- Carbon has many forms (allotropes): diamond, graphite, activated carbon, fullerene.
- Allotropes — same element but different properties/physical forms.
Application & Calculations
- To find molar mass: Multiply the number of each element by its mass, then total.
- Example: Baking soda (NaHCO3): Na=22, H=1, C=12, O=16x3 = 48; total = 84 g/mole.
Atomic Structure & Isotopes
- Nucleus is composed of protons and neutrons (nucleons).
- Isotopes — same number of protons but different neutrons.
- Isotones — same neutrons.
- Isoelectronic — same electrons.
Key Terms & Definitions
- Mass — weight of a substance.
- Mole — number of particles (Avogadro’s number: 6.02 x 10²³).
- Atomic mass unit (AMU) — unit of atom weight.
- Molar mass — weight of one mole (grams/mole).
- Formula mass — weight of the formula unit of an ionic compound.
- Isotope — atoms of the same element but different neutrons.
- Allotrope — different forms of an element.
Action Items / Next Steps
- Answer and complete the table in the notebook: element, molecule, compound.
- Familiarize yourself with the positions of the groups in the periodic table.
- Learn the molar mass of some common compounds using the periodic table.
- Rest for 30 minutes; return to class at 8:45 for computations.