Overview
This lecture covers atomic structure, properties of elements and molecules, bonding types, chemical reactions, water's unique properties, solutions, acids and bases, and fundamental chemistry terminology.
Subatomic Particles and Atomic Structure
- Atoms consist of protons (+, nucleus, ½ mass), neutrons (neutral, nucleus, ½ mass), and electrons (–, shells, negligible mass).
- The nucleus is the atom's center; electron shells surround the nucleus at varying distances.
- Atomic number = number of protons; atomic mass = protons + neutrons.
- Neutrons = atomic mass – atomic number; atomic mass = protons + neutrons.
Elements in Biology
- Element: pure substance, cannot be chemically broken down.
- 4 primary elements in the human body: carbon, oxygen, hydrogen, nitrogen.
- Trace elements make up 0.1% of the body.
Isotopes and Ions
- Isotopes have same protons, different neutrons, altering atomic mass.
- Ions have unequal protons and electrons, resulting in charge.
- Cation: positive ion (fewer electrons), Anion: negative ion (more electrons).
Electron Configuration and Periodic Table Trends
- First shell holds 2 electrons, second and third hold 8 each.
- Valence shell: outermost shell; valence electrons determine reactivity.
- Same column: same valence electrons; same row: same number of shells.
- Electronegativity: an atom's pull on electrons; increases left→right and bottom→top.
Molecules and Compounds
- Molecule: two or more atoms bonded; compound: molecule with different elements.
- Organic compounds contain carbon covalently bonded to O, H, or N.
- Depiction methods: molecular name, formula, Lewis and dot structure, structural formula.
Isomers
- Isomer: same atoms, different arrangement and properties.
Chemical Bonds
- Covalent bonds: atoms share electrons (non-polar: equal, polar: unequal).
- Ionic bonds: electrons transferred, forming oppositely charged ions.
- Hydrogen bonds: attraction between molecules with polar covalent bonds; weaker than covalent and ionic.
- Number and type of bonds depend on valence electrons and electronegativity.
Chemical Reactions and Equilibrium
- Chemical reactions rearrange atoms, follow Law of Conservation of Matter.
- Reactants → products; reactions can be reversible (↔) or not (→).
- Equilibrium: forward and reverse reaction rates are equal.
- Reaction rate increases with temperature, reactant concentration, or enzymes.
Water’s Properties
- Water is polar, forms hydrogen bonds, exhibits cohesion, adhesion, high specific heat, and solvent abilities.
- Ice is less dense than liquid water due to molecular structure; ice floats, affecting environments.
- Temperature measures kinetic energy; in solids, particles move slower and are denser (except ice).
Solutions, Acids, and Bases
- Solution: solvent (dissolving substance) + solute (dissolved substance).
- Concentration: amount of solute in solution, often measured in molarity.
- Acids donate H+, bases accept H+; pH is inversely related to H+ concentration.
- Buffers resist pH change by absorbing or releasing H+ ions.
Key Terms & Definitions
- Proton — positively charged subatomic particle in the nucleus.
- Neutron — neutral subatomic particle in the nucleus.
- Electron — negatively charged subatomic particle in electron shells.
- Element — substance made of one type of atom.
- Compound — molecule containing atoms of different elements.
- Trace Element — element needed in minute amounts.
- Isotope — atom with same protons, different neutrons.
- Ion — atom with unequal protons and electrons, carries charge.
- Cation — positively charged ion.
- Anion — negatively charged ion.
- Molecule — two or more atoms bonded together.
- Covalent Bond — bond where atoms share electrons.
- Non-Polar Covalent Bond — equal sharing of electrons.
- Polar Covalent Bond — unequal sharing of electrons.
- Ionic Bond — electron transfer creates charged ions.
- Hydrogen Bond — weak attraction between polar molecules.
- Electronegativity — atom's tendency to attract electrons.
- Valence Shell — outermost electron shell.
- Valence Electron — electron in the valence shell.
- Isomer — molecules with same formula, different arrangement.
- Reactant — starting substance in a reaction.
- Product — result of a chemical reaction.
- Enzyme — protein catalyst for chemical reactions.
- Reaction equilibrium — state when forward and reverse reaction rates are equal.
Action Items / Next Steps
- Review periodic table trends and element properties.
- Practice calculating atomic mass, neutrons, and ionic charges.
- Draw and interpret molecular formulas, Lewis structures, and structural formulas.
- Memorize definitions and characteristics of key bond types.
- Review the special properties of water and be able to give examples.