Introduction to Chemistry Lecture

Periodic Table

Names of Elements in Groups

• Column 1: Hydrogen, lithium, sodium, potassium, rubidium (alkali metals)
  • Hydrogen is a non-metal; others are alkali metals
  • Alkali metals: Very reactive, one valence electron, form +1 ions
• Column 2: Beryllium, magnesium, calcium, strontium, barium (alkaline earth metals)
  • Reactive, but less than alkali metals
  • Two valence electrons, form +2 ions

Transition Metals (Groups 3-12)

• Examples: Scandium, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, zinc
• Variable charges (e.g., Fe: +2 or +3, Cu: +1 or +2)
• Some common charges (e.g., Zn: +2, Ag: +1)

Inner Transition Metals

• Lanthanides and actinides

Other Groups

• Group 13: Boron, aluminum, gallium, indium, thalium (form +3 ions often)
• Group 14: Carbon, silicon, germanium, tin, lead (form +2 or +4 ions)
• Group 15: Nitrogen, phosphorus, arsenic, antimony, bismuth (form -3 ions)
• Group 16: Oxygen, sulfur, selenium, tellurium, polonium (form -2 ions, known as chalcogens)
• Group 17: Fluorine, chlorine, bromine, iodine, astatine (form -1 ions, halogens)
• Group 18: Helium, neon, argon, krypton, xenon, radon (noble gases, chemically inert)

Properties

• Electronegativity increases towards fluorine (most reactive non-metal)
• Metallic character increases down and to the left of the periodic table

Metalloids

• Common metalloids: Silicon, germanium, arsenic, etc.
• Properties: Conduct a small amount of electricity, not as well as metals

Some Key Points

• Metals: Conduct electricity and heat, malleable, ductile
• Non-metals: Insulators
• Metalloids: Intermediate properties

Bonding

Ionic Bonds

• Involves transfer of electrons
• Formed between metals and non-metals
• Example: Sodium (Na) and chlorine (Cl) form NaCl

Covalent Bonds

• Involves sharing of electrons
• Can be non-polar (equal sharing) or polar (unequal sharing)
• Example: Hydrogen (H) and fluorine (F) form HF (polar covalent bond)

Types of Compounds

Ionic Compounds

• Typically between metals and non-metals
• Example: MgO (Magnesium oxide)

Molecular Compounds

• Typically between non-metals
• Example: CO2 (Carbon dioxide)

Ammonium Compounds

• Contain ionic and covalent bonds
• Example: NH4Cl (Ammonium chloride)

Atomic Structure

Subatomic Particles

• Protons (+, in nucleus)
• Neutrons (neutral, in nucleus)
• Electrons (-, in energy levels)

Key Terms

• Valence electrons: Outermost electrons involved in chemical bonding
• Core electrons: Inner electrons

Isotopes vs Allotropes

• Isotopes: Same element, different mass numbers (e.g., Carbon-12 and Carbon-13)
• Allotropes: Different structural forms of the same element (e.g., Diamond and graphite for Carbon)

Example Calculations

• Finding number of protons, neutrons, electrons: Use atomic number and mass number

Types of Elements (Quiz)

• Transition Metal: Fe (Iron)
• Most Reactive Metal: Li (Lithium)
• Non-metal: Br (Bromine)
• Alkaline Earth Metal: Mg (Magnesium)
• Three Valence Electrons: Al (Aluminum)

Diatomic Elements

• H₂, N₂, O₂, F₂, Cl₂, Br₂, I₂
• Forms at room temperature: H₂ (gas), N₂ (gas), O₂ (gas), F₂ (gas), Cl₂ (green gas), Br₂ (red liquid), I₂ (purple solid)

Chemical Reactions

Combustion Reactions

• Products: CO₂ and H₂O
• Example: Propane (C₃H₈) + O₂ → CO₂ + H₂O

Combination Reactions

• Two or more reactants combine to form one product
• Example: Zn + Br₂ → ZnBr₂

Decomposition Reactions

• One reactant breaks down into two or more products
• Example: CaCO₃ → CaO + CO₂

Single Replacement Reactions

• One element replaces another in a compound
• Example: Al + HCl → AlCl₃ + H₂

Double Replacement Reactions

• Exchange of ions between two compounds
• Example: AgNO₃ + MgCl₂ → AgCl + Mg(NO₃)₂

Unit Conversion

Distance Units

• Example: 1 mile = 5280 feet, 1 kilometer = 1000 meters

Volume and Mass Units

• Example: 1 liter = 1000 milliliters, 1 kilogram = 1000 grams

Time Units

• Example: 1 year = 365 days, 1 minute = 60 seconds

Example Conversion Problems

• Converting meters to kilometers, millimeters to centimeters, etc.

Metric System Prefixes

Common Prefixes

• Terra (10¹²), Giga (10⁹), Mega (10⁶), Kilo (10³), etc.
• Example: 1 kilometer = 10³ meters

Example Conversion Problems

• Trying different conversions using metric system prefixes

Density Calculations

Density Equation

• Density = Mass / Volume

Example Problem

• Volume displacement method for finding the volume of an irregular object

Significant Figures

Rules

• Non-zero numbers are always significant
• Leading zeros are not significant
• Trailing zeros are significant if they are after a decimal point
• Example Problems: Identifying significant figures in given numbers

Rounding Rules

• Multiplication/Division: Least number of significant figures
• Addition/Subtraction: Least number of decimal places

Example Problems

• Performing operations and rounding to the correct number of significant figures

Naming Compounds

Ionic Compounds

• Metal + Non-metal (ending in -ide)
• Example: NaCl (Sodium chloride)

Molecular Compounds

• Non-metal + Non-metal (using prefixes like mono-, di-, tri-)
• Example: PCl₅ (Phosphorus pentachloride)

Acids

• Binary Acids (Hydro + root + -ic acid)
  • Example: HCl (Hydrochloric acid)
• Oxyacids (root + -ic acid if anion ends in -ate, -ous acid if anion ends in -ite)
  • Example: H₂SO₄ (Sulfuric acid)

Chemical Calculations

Moles and Molar Mass

• Molar Mass: Mass of one mole of a substance (grams per mole)
• Example: Molar mass of H₂O = 18 g/mol

Converting Grams to Moles

• Use molar mass as a conversion factor
• Example: Converting 48 grams of carbon to moles

Percent Composition by Mass

• (Mass of element in 1 mole of compound / Molar mass of compound) × 100%
• Example: Percent composition of carbon in CH₄

Avogadro's Number

• 1 mole = 6.02 × 10²³ particles (atoms, molecules)

Practical Applications

Density Application

• Calculating densities of different materials and converting units

Unit Conversions for Speed, Volume, Area

• Example Problems: Converting meters per second to miles per hour, cubic meters to cubic centimeters, etc.

Balancing Chemical Reactions

General Steps

• Balance elements one at a time
• Save hydrogen and oxygen for last
• Adjust coefficients as needed to balance each element

Example Balancing Problems

• Balancing combustion, combination, decomposition, single replacement, and double replacement reactions

Identifying Redox Reactions

• Look for changes in oxidation states and presence of pure elements

Further Resources

• Additional videos on stoichiometry, molarity calculations, dilution problems, etc.