Introductory Chemistry

Jul 20, 2024

Introduction to Chemistry Lecture Notes

In this lecture, we focused on key concepts in chemistry, particularly centered around the periodic table, chemical bonds, atomic structure, and types of chemical reactions. Below is a summary capturing the essential points and details.

Periodic Table Overview

  • Know the names and properties of elements. Key groups:
    • Group 1 (Alkali Metals): H (Hydrogen), Li (Lithium), Na (Sodium), K (Potassium), Rb (Rubidium), Cs (Cesium)
      • Alkali metals are very reactive, form ions with +1 charge, and have 1 valence electron.
    • Group 2 (Alkaline Earth Metals): Be (Beryllium), Mg (Magnesium), Ca (Calcium), Sr (Strontium), Ba (Barium)
      • Reactive, but less so than alkali metals, form ions with +2 charge, and have 2 valence electrons.
    • Transition Metals: Sc (Scandium), Ti (Titanium), V (Vanadium), Cr (Chromium), Mn (Manganese), Fe (Iron), Co (Cobalt), Ni (Nickel), Cu (Copper), Zn (Zinc), etc.
      • Can have multiple oxidation states (e.g., Iron: +2 or +3, Copper: +1 or +2).
    • Groups 13-18: Representative elements, including boron group, carbon group, nitrogen group, chalcogens (oxygen group), halogens, and noble gases.
      • Group characteristics and common oxidation states were discussed.

Types of Bonds

  • Ionic Bonds: Transfer of electrons between metals and non-metals, forming cations and anions (e.g., NaCl).
  • Covalent Bonds: Sharing of electrons between non-metals. Can be polar (unequal sharing) or nonpolar (equal sharing).
  • Lewis Structures: Diagram showing bonding between atoms — metals tend to give away electrons, nonmetals accept electrons.

Atomic Structure

  • Atomic Number (Z): Number of protons defining the element.
  • Mass Number (A): Sum of protons and neutrons in the nucleus.
  • Isotopes: Atoms of the same element (same Z) but with different neutrons (thus different A)
  • Electron Configuration: Distribution of electrons across different energy levels around the nucleus.

Examining Ions

  • Calculating number of protons, neutrons, and electrons in atoms and ions.
  • Determining valence electrons and core electrons.
  • Isotope abundance and average atomic mass calculations.

Chemical Reactions

  • Combustion Reactions: Hydrocarbons reacting with O2 to produce CO2 and H2O.
  • Redox Reactions: Transfer of electrons, identified by change in oxidation states.
  • Single Replacement Reactions: Element reacts with a compound, swapping places with a constituent element of the compound.
  • Double Replacement Reactions: Exchange of ions between two compounds, e.g., producing a precipitate, acid-base neutralizations (not redox by themselves).
  • Decomposition Reactions: Single compound breaking down into two or more simpler products.

Molar Mass and Stoichiometry

  • Molar Mass: Mass in grams of one mole of any element or compound calculated based on atomic masses from the periodic table.
  • Conversions: Converting between grams, moles, and number of atoms/molecules using Avogadro’s number (6.022 x 10^23).
  • Calculating Mass Percent: Percentage composition of elements in a compound.

Lewis Structures and Molecular Geometry

  • Drawing Lewis structures for molecules.
  • Identifying shapes of molecules and predicting bond angles based on VSEPR theory (not explicitly covered but useful knowledge).

Properties and Classification of Elements

  • Metals, Non-metals, and Metalloids: Conductivity, appearance, and physical state differences.
  • Noble Gases: Chemically inert due to having a complete electron configuration.
  • Recognizing diatomic elements, common allotropes, etc.

Chemical Naming Conventions

  • Ionic Compounds: Named using the metal first and the non-metal with ‘ide’ suffix (NaCl: Sodium Chloride).
  • Covalent Compounds: Use prefixes to denote number of atoms (CO2: Carbon Dioxide)
  • Acids: Hydro prefix and ic/ous suffix depending on the presence of oxygen. (HCl: Hydrochloric Acid vs. H2SO4: Sulfuric Acid).

Practice Questions

  • Various practice questions on converting units, identifying reaction types, balancing chemical equations, and naming compounds.
  • Important concepts of physical and chemical properties of elements and compounds.

Conclusion

  • This lecture provides a solid foundation for understanding the periodic table, chemical bonding, atomic structure, and types of reactions necessary for succeeding in a chemistry course.