General Chemistry: Foundations, Atoms, Elements, Molecules, and Compounds – Study Guide

Equation Sheet and Reference Data

Potentially Useful Equations

• Density: The density (d) of a substance is defined as its mass (m) per unit volume (V).

$d = \frac{m}{V}$

• Atomic Mass: The average atomic mass of an element is calculated using the relative abundance and mass of each isotope.

$\text{Atomic mass} = \sum (\text{fraction of isotope} \times \text{mass of isotope})$

• Avogadro's Number: The number of particles (atoms, molecules, ions) in one mole of a substance.

$1 \text{ mole} = 6.022 \times 10^{23} \text{ particles}$

Periodic Table of the Elements

• The periodic table organizes elements by increasing atomic number and groups elements with similar chemical properties into columns (groups/families).

• Key information includes element symbol, atomic number, and typical ionic charges.

Chapter 1: Matter, Measurement, and Scientific Approach

Scientific Approach: Theories and Laws

• Scientific Law: A concise statement that summarizes observed phenomena.

• Theory: A well-substantiated explanation of some aspect of the natural world.

• Hypothesis: A tentative explanation that can be tested by experiments.

States of Matter and Classification

• States of Matter: Solid (definite shape and volume), liquid (definite volume, indefinite shape), gas (indefinite shape and volume).

• Pure Substances: Elements and compounds with fixed composition.

• Mixtures: Homogeneous (uniform composition) and heterogeneous (non-uniform composition).

Physical and Chemical Properties and Changes

• Physical Properties: Observed without changing the substance (e.g., melting point, density).

• Chemical Properties: Describe how a substance reacts (e.g., flammability).

• Physical Change: Does not alter chemical composition (e.g., melting ice).

• Chemical Change: Alters chemical composition (e.g., rusting iron).

Energy: Law of Conservation and Types

• Law of Conservation of Energy: Energy cannot be created or destroyed, only transformed.

• Kinetic Energy: Energy of motion.

• Potential Energy: Energy due to position or composition.

Measurement and SI Prefixes

• SI Units: Standard units for scientific measurement (meter, kilogram, second, mole, etc.).

• Common SI Prefixes: kilo- (103), milli- (10-3), centi- (10-2).

Density Calculations

• Density is used to relate mass and volume for substances.

• Units: g/mL (liquids), g/cm3 (solids).

Significant Figures and Precision

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

• Rules: Nonzero digits are always significant; zeros between nonzero digits are significant; leading zeros are not significant; trailing zeros are significant if there is a decimal point.

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

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

Dimensional Analysis

• Method for converting between units using conversion factors.

• Always include units in calculations to ensure correctness.

Chapter 2: Atoms and Elements

Atomic Theory and Structure

• Dalton's Atomic Theory: Elements are composed of atoms; atoms of the same element are identical; atoms combine in simple ratios to form compounds.

• Nuclear Theory: Atoms have a dense nucleus containing protons and neutrons; electrons occupy the surrounding space.

Subatomic Particles

• Proton: Positively charged particle in the nucleus.

• Neutron: Neutral particle in the nucleus.

• Electron: Negatively charged particle outside the nucleus.

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

• Mass Number (A): Total number of protons and neutrons.

Isotopes and Atomic Mass

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

• Average Atomic Mass: Weighted average of all isotopes' masses.

Ions

• Cation: Atom that has lost electrons (positive charge).

• Anion: Atom that has gained electrons (negative charge).

Periodic Table Organization

• Groups/Families: Columns with similar chemical properties.

• Periods: Rows indicating energy levels.

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

• Transition Elements: Middle section of the table, often with variable charges.

Atomic Mass Calculations

• Use isotopic abundance and mass to calculate average atomic mass.

• Example: If isotope X-45 (32.88%, 44.876 amu) and X-47 (67.12%, 46.964 amu):

$\text{Average mass} = (0.3288 \times 44.876) + (0.6712 \times 46.964)$

Mole Concept and Avogadro's Number

• 1 mole = 6.022 × 1023 particles.

• Used to convert between mass, number of particles, and moles.

Chapter 3: Molecules and Compounds

Types of Chemical Bonds

• Ionic Bonds: Electrostatic attraction between cations and anions (usually metal + nonmetal).

• Covalent Bonds: Sharing of electrons between nonmetals.

Chemical Formulas

• Empirical Formula: Simplest whole-number ratio of elements in a compound.

• Molecular Formula: Actual number of atoms of each element in a molecule.

• Structural Formula: Shows how atoms are connected.

Naming Compounds

• Ionic Compounds: Name cation first, then anion (e.g., NaCl = sodium chloride).

• Covalent Compounds: Use prefixes to indicate number of atoms (e.g., CO2 = carbon dioxide).

• Acids: Binary acids (hydro- prefix), oxyacids (based on polyatomic ions).

Polyatomic Ions

• Common polyatomic ions include sulfate (SO42-), nitrate (NO3-), ammonium (NH4+), etc.

Calculating Molar Mass and Conversions

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

• Used to convert between grams, moles, and number of particles.

Percent Composition and Empirical Formulas

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

• Empirical Formula: Determined from percent composition by converting mass to moles and finding the simplest ratio.

SI Prefixes Table

Prefix	Symbol	Factor
kilo-	k	103
centi-	c	10-2
milli-	m	10-3

Sample Practice Questions (Selected)

• Scientific Approach: Experiments that confirm a hypothesis can lead to a theory; a law summarizes related observations.

• States of Matter: Solids have definite shape and volume; liquids have definite volume but indefinite shape; gases have neither.

• Significant Figures: The number of significant figures in a measurement depends on the precision of the instrument.

• SI Prefixes: The symbol for 103 is 'k' (kilo-).

• Atomic Structure: The mass number is the sum of protons and neutrons; atomic number is the number of protons.

• Isotopes: Isotopes of the same element have the same number of protons but different numbers of neutrons.

• Mole Calculations: Use Avogadro's number to convert between moles and number of atoms or molecules.

• Empirical Formula: Determined from percent composition by converting mass to moles and finding the simplest ratio.

• Naming Compounds: Know how to name ionic and covalent compounds, acids, and use polyatomic ions.

Additional info:

• This study guide is based on a practice exam and review sheet for a General Chemistry I course, covering foundational topics in matter, measurement, atomic structure, the periodic table, and chemical compounds.

• For detailed practice, refer to the provided practice questions and answer key.