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

Study Guide - Smart Notes

Tailored notes based on your materials, expanded with key definitions, examples, and context.

Chapter 1: Foundations of Chemistry

Differences Between Atoms and Molecules

Atoms are the basic units of matter, consisting of protons, neutrons, and electrons. Molecules are combinations of two or more atoms bonded together chemically.

Atom: The smallest unit of an element that retains its chemical properties.
Molecule: A group of atoms bonded together, representing the smallest fundamental unit of a chemical compound.
Example: O2 is a molecule made of two oxygen atoms.

States and Compositions of Matter

Matter exists in different physical states and can be classified by its composition.

States: Solid, liquid, gas.
Compositions: Elements, compounds, mixtures.
Example: Water (H2O) is a compound; air is a mixture.

Physical vs. Chemical Changes/Properties

Physical Change: Alters the form or appearance but not the composition (e.g., melting ice).
Chemical Change: Alters the composition, forming new substances (e.g., rusting iron).
Physical Property: Can be observed without changing the substance (e.g., boiling point).
Chemical Property: Describes how a substance reacts (e.g., flammability).

Types of Energy; Principles of Energy

Kinetic Energy: Energy of motion.
Potential Energy: Stored energy due to position or composition.
Law of Conservation of Energy: Energy cannot be created or destroyed, only transformed.

Scientific Approach

Observation → Hypothesis → Experiment → Theory → Law
Scientific method involves systematic investigation and reasoning.

SI Base Units

Length: meter (m)
Mass: kilogram (kg)
Time: second (s)
Temperature: kelvin (K)
Amount of substance: mole (mol)

Temperature Scales

Celsius (°C), Kelvin (K), Fahrenheit (°F)
Conversion:
Conversion:

Unit Conversions and Prefix Multipliers

Unit conversions are essential for solving chemistry problems. Prefix multipliers indicate powers of ten.

Common Prefixes: kilo- (103), centi- (10-2), milli- (10-3), micro- (10-6), nano- (10-9), pico- (10-12), etc.
Example: 1 kilometer (km) = 1000 meters (m)
Know how to convert between units using conversion factors.

Significant Figures (Sig Figs)

Definition: 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 only if there is a decimal point.
Calculations:
- For multiplication/division: answer has the same number of sig figs as the measurement with the fewest sig figs.
- For addition/subtraction: answer has the same number of decimal places as the measurement with the fewest decimal places.
Example: 2.30 × 4.0 = 9.2 (2 sig figs)

Measurement Accuracy and Precision

Accuracy: How close a measurement is to the true value.
Precision: How close repeated measurements are to each other.
Example: Hitting the bullseye (accuracy); grouping of darts (precision).

Chapter 2: Atoms and Elements

Atoms vs. Elements

Elements are pure substances consisting of only one type of atom. Atoms are the smallest units of elements.

Element: Defined by its number of protons (atomic number).
Example: Gold (Au) is an element; a gold atom is a single particle of gold.

Atomic Theory and Models

Dalton's Atomic Theory: All matter is made of atoms; atoms of the same element are identical; atoms combine in simple ratios to form compounds.
Modern Model: Atoms consist of a nucleus (protons and neutrons) and electrons in orbitals.

Law of Definite Proportions

Definition: A chemical compound always contains the same elements in the same proportion by mass.
Example: Water (H2O) always has 2 hydrogen atoms for every 1 oxygen atom.

Subatomic Particles

Proton: Positive charge, found in nucleus.
Neutron: No charge, found in nucleus.
Electron: Negative charge, found outside nucleus.
Atomic Number (Z): Number of protons.
Mass Number (A): Number of protons + neutrons.
Isotopes: Atoms of the same element with different numbers of neutrons.

Atomic Mass and the Periodic Table

Atomic Mass: Weighted average mass of all isotopes of an element.
Periodic Table: Organizes elements by increasing atomic number; shows trends in properties.
Groups: Columns (elements with similar properties).
Periods: Rows.

Conversions Involving Moles

Mole: The amount of substance containing particles (Avogadro's number).
Conversions:
- Mass to moles:
- Moles to number of atoms:
Example: 18 g of H2O contains 1 mole of water molecules.

Summary Table: Subatomic Particles

Particle	Symbol	Charge	Location	Relative Mass
Proton	p+	+1	Nucleus	1
Neutron	n0	0	Nucleus	1
Electron	e-	-1	Outside nucleus	1/1836