Exam 1 Review: Measurements, Atoms, Compounds, and Chemical Reactions (GOB Chemistry)

Exam 1 Review: Key Topics

• Measurements and Problem Solving

• Atoms & Elements

• Ionic & Molecular Compounds & Chemical Equations

• Chemical Quantities and Reactions

Chapter 2: Measurements and Problem Solving

Types of Measurements

Measurements in chemistry are essential for quantifying substances and understanding chemical processes.

• Qualitative Measurements: Describe qualities or characteristics (e.g., color, texture).

• Quantitative Measurements: Involve numbers and units (e.g., mass, volume).

Units and Uncertainty

• SI Units: Standard units used in science (meter, kilogram, second, mole, etc.).

• Uncertainty: All measurements have some degree of uncertainty due to instrument limitations.

• Accuracy: How close a measurement is to the true value.

• Precision: How close repeated measurements are to each other.

Scientific Notation and Significant Figures

• Scientific Notation: Expresses numbers as a product of a coefficient and a power of ten (e.g., $6.02 \times 10^{23}$).

• Significant Figures: Digits in a measurement that are known with certainty plus one estimated digit.

Metric System and Multipliers

• Metric Prefixes: Used to express multiples or fractions of units (e.g., kilo-, centi-, milli-).

Common Measurements

• Volume: Measured in liters (L) or milliliters (mL).

Problem Solving: Conversion and Dimensional Analysis

• Conversion Factors: Ratios used to convert from one unit to another.

• Dimensional Analysis: A method to solve problems using conversion factors to ensure units cancel appropriately.

Intensive and Extensive Properties

• Intensive Property: Does not depend on the amount of substance (e.g., density).

• Extensive Property: Depends on the amount of substance (e.g., mass, volume).

Chapter 4: Atoms & Elements

Atomic Theory

The atomic theory explains the nature of matter by stating that all matter is composed of atoms.

• Atoms: The smallest unit of an element that retains its properties.

• Subatomic Particles: Protons (positive), neutrons (neutral), electrons (negative).

Atomic Number and Mass Number

• Atomic Number (Z): Number of protons in the nucleus; defines the element.

• Mass Number (A): Total number of protons and neutrons ($A = Z + N$).

Isotopes and Element Symbols

• Isotopes: Atoms of the same element with different numbers of neutrons.

• Element Symbol: One- or two-letter abbreviation for an element (e.g., H for hydrogen).

Periodic Table Organization

• Groups/Families: Vertical columns; elements with similar properties.

• Periods: Horizontal rows.

• Main Group Elements (A): Groups 1A-8A.

• Transition Metals (B): Groups in the center of the table.

• Metals, Nonmetals, Metalloids: Classified by physical and chemical properties.

Common Element Groups

• Alkali Metals (1A)

• Alkaline Earth Metals (2A)

• Halogens (7A)

• Noble Gases (8A)

Monatomic Ions

• Cations: Positively charged ions (usually metals).

• Anions: Negatively charged ions (usually nonmetals).

Chapter 6: Ionic & Molecular Compounds and Chemical Nomenclature

Compounds and Formulas

• Compounds: Substances formed from two or more elements chemically combined.

• Chemical Formula: Shows the types and numbers of atoms in a compound (e.g., H2O).

Ions and Ionic Compounds

• Cations: Type 1 (fixed charge) and Type 2 (variable charge, transition metals).

• Anions: Usually nonmetals, end in "-ide".

• Naming Ionic Compounds:

  • Type 1: Cation + Anion (e.g., NaCl: sodium chloride)

  • Type 2: Cation (charge in Roman numerals) + Anion (e.g., FeCl2: iron(II) chloride)

Polyatomic Ions

• Groups of atoms with a charge (e.g., SO42-, NO3-).

Acids and Naming

• Binary Acids: Hydrogen + nonmetal (e.g., HCl: hydrochloric acid).

• Oxoacids: Hydrogen + polyatomic ion (e.g., HNO3: nitric acid).

• Naming Patterns:

  • "-ate" → "-ic acid" (e.g., sulfate → sulfuric acid)

  • "-ite" → "-ous acid" (e.g., sulfite → sulfurous acid)

  • "per-...-ate" → "per-...-ic acid"

  • "hypo-...-ite" → "hypo-...-ous acid"

Molecular Compounds

• Naming: Prefix + 1st atom + prefix + 2nd atom (ending in "-ide").

• Prefixes: mono-, di-, tri-, tetra-, penta-, etc.

• Example: CO2 is carbon dioxide.

Avogadro's Number and Molar Mass

• Avogadro's Number: $6.02 \times 10^{23}$ units/mol.

• Molar Mass: Mass of one mole of a substance (g/mol).

• Formula Weight: Sum of atomic weights in a formula.

Percent Composition

• Percent Composition: Percent by mass of each element in a compound.

• Empirical Formula: Simplest whole-number ratio of atoms.

• Molecular Formula: Actual number of atoms of each element.

• Calculation: $\text{Percent Composition} = \frac{\text{Mass of Element}}{\text{Total Mass of Compound}} \times 100$

Lewis Structures and Covalent Bonding

• Lewis Structures: Diagrams showing valence electrons and bonding in molecules.

• Octet Rule: Atoms tend to have 8 electrons in their valence shell.

• Bond Types:

  • Single Bond: 1 shared pair of electrons

  • Double Bond: 2 shared pairs

  • Triple Bond: 3 shared pairs

• Electronegativity: Tendency of an atom to attract electrons in a bond.

• Bond Polarity: Difference in electronegativity leads to polar or nonpolar bonds.

• Molecular Shape: Determined by electron pair geometry (VSEPR theory).

Chapter 7: Chemical Reactions and Quantities

Chemical Reactions and Equations

• Chemical Change: Substances are transformed into new substances.

• Chemical Equation: Represents a chemical reaction using symbols and formulas.

• Law of Conservation of Matter: Matter is neither created nor destroyed in a chemical reaction.

• Balancing Equations: Ensures the same number of each atom on both sides of the equation.

Types of Chemical Reactions

• Combination (Synthesis): $A + B \rightarrow AB$

• Decomposition: $AB \rightarrow A + B$

• Combustion: $C_xH_yO_z + O_2 \rightarrow CO_2 + H_2O$

• Redox (Oxidation-Reduction): Involves electron transfer; LEO (Lose Electrons = Oxidation), GER (Gain Electrons = Reduction).

• Single Displacement: $A + BC \rightarrow AC + B$

• Double Displacement: $AB + CD \rightarrow AD + CB$

Stoichiometry and Reaction Quantities

• Stoichiometry: The calculation of reactants and products in chemical reactions.

• Mole Ratios: Derived from coefficients in balanced equations.

• Stoichiometric Conversions: Use mole ratios to convert between amounts of reactants and products.

• General Steps:

  1. Grams A $\rightarrow$ Moles A

  2. Moles A $\rightarrow$ Moles B (using mole ratio)

  3. Moles B $\rightarrow$ Grams B

• Limiting Reagent: The reactant that is completely consumed first, limiting the amount of product formed.

• Theoretical Yield: Maximum amount of product possible from given reactants.

• Percent Yield: $\text{Percent Yield} = \frac{\text{Actual Yield}}{\text{Theoretical Yield}} \times 100$

Appendix: Common Polyatomic Ions (Table)

Name	Formula	Charge
Ammonium	NH4+	+1
Nitrate	NO3-	-1
Sulfate	SO42-	-2
Phosphate	PO43-	-3
Hydroxide	OH-	-1
Carbonate	CO32-	-2

Additional info: Some content and explanations have been expanded for clarity and completeness based on standard GOB Chemistry curriculum.