General Chemistry Exam 1 Study Guide: Matter, Measurement, Atoms, and Periodic Properties

Exam 1 Study Guide: General Chemistry

Chapter 1 – Matter, Energy, and Measurements

This chapter introduces the foundational concepts of chemistry, focusing on the nature of matter, the importance of measurement, and the use of significant figures in calculations.

• Performing Arithmetic with Significant Figures: Calculations in chemistry must reflect the precision of the measured values. The number of significant figures in the result should match the least precise measurement used in the calculation.

• Precision vs. Accuracy:

  • Precision refers to how closely repeated measurements agree with each other.

  • Accuracy refers to how close a measurement is to the true or accepted value.

• Extensive and Intensive Properties of Matter:

  • Extensive properties depend on the amount of matter (e.g., mass, volume).

  • Intensive properties do not depend on the amount of matter (e.g., density, temperature).

• Dimensional Analysis: A method for converting between units using conversion factors.

  • Use conversion factors (ratios) to convert units.

  • Always keep track of units throughout calculations.

  • Example: To convert 10 inches to centimeters, use the conversion factor $1\ \text{inch} = 2.54\ \text{cm}$.

• Significant Figures in Answers: The final answer should reflect the correct number of significant figures based on the input data.

Chapter 2 – Atoms, Molecules, and Ions

This chapter covers the structure of atoms, the organization of the periodic table, and the basics of chemical nomenclature and formulas.

• Identifying Metals vs. Non-metals: Metals are typically found on the left and center of the periodic table, while non-metals are on the right.

• Interpreting Chemical Symbols: Each element is represented by a unique one- or two-letter symbol (e.g., H for hydrogen, O for oxygen).

• Ions:

  • Cations are positively charged ions (loss of electrons).

  • Anions are negatively charged ions (gain of electrons).

  • Predict charge from number of protons and electrons.

  • Predict number of protons/electrons from charge and chemical symbol.

• Periodic Properties:

  • Periodic Table Organization: Elements are arranged by increasing atomic number.

  • Groups and Periods:

    • Groups (columns) share similar chemical properties.

    • Periods (rows) indicate increasing energy levels.

  • Major Groups:

    • Metals, non-metals, metalloids

    • Alkali metals, alkaline earth metals, chalcogens, halogens, noble gases

  • Periodic Trends:

    • Atomic radius, ionization energy, electron affinity, etc.

    • Example: Atomic radius decreases across a period and increases down a group.

• Naming Molecular and Ionic Compounds:

  • Know how to name molecular compounds from formulas and write formulas from names.

  • Know names and charges of common cations and anions.

  • Example: NaCl is sodium chloride; CO2 is carbon dioxide.

• Calculating Average Atomic Mass:

  • Weighted average of the masses of an element's isotopes.

  • Formula: $\text{Average Atomic Mass} = \sum (\text{isotope mass} \times \text{fractional abundance})$

• Properties of Subatomic Particles:

  • Proton: Positive charge, mass ≈ 1 amu

  • Neutron: No charge, mass ≈ 1 amu

  • Electron: Negative charge, mass ≈ 0.0005 amu

• Empirical vs. Molecular Formulas:

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

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

  • To find empirical formula, reduce the molecular formula to the lowest whole-number ratio.

  • Example: The molecular formula of glucose is C6H12O6; its empirical formula is CH2O.

Table: Classification of Elements and Groups

Group Name	Location on Periodic Table	Common Properties
Alkali Metals	Group 1	Highly reactive, 1 valence electron, form +1 ions
Alkaline Earth Metals	Group 2	Reactive, 2 valence electrons, form +2 ions
Halogens	Group 17	Very reactive non-metals, form -1 ions
Noble Gases	Group 18	Inert, very low reactivity, full valence shell
Transition Metals	Groups 3-12	Variable oxidation states, often form colored compounds

Additional info: This study guide is based on an exam outline and covers the essential topics for the first exam in a General Chemistry course, including measurement, atomic structure, periodic trends, and chemical nomenclature.