CHEM-132 Exam 1 Study Guide: Chapters 1-3 Flashcards

Chapter 1: Matter and Measurement

States of Matter:
- Solid: Characterized by a fixed shape and a fixed volume.
- Liquid: Characterized by a fixed volume, but takes the shape of its container.
- Gas: Has no fixed shape and no fixed volume; expands completely to fill its container.
- Plasma: Consists of an ionized gas (typically excluded from testing at this introductory level).
Physical vs. Chemical Properties and Changes:
- Physical Properties: Properties that can be observed or measured without altering the chemical identity of the substance (e.g., color, melting point, density, solubility).
- Physical Changes: Changes in form or state that maintain the original chemical identity (e.g., phase changes, dissolving salt in water, tearing paper).
- Chemical Properties: Properties observed only through a chemical reaction that changes the identity of the substance (e.g., reactivity, flammability, ability to rust).
- Chemical Changes: Processes that result in the creation of new chemical substances (e.g., combustion, rusting, chemical decomposition, neutralization).
Separation Techniques:
- Distillation: Separates liquid mixtures based on differences in boiling points.
- Filtration: Separates an insoluble solid component from a liquid component.
- Crystallization: Separates a dissolved solid from a solution by evaporating the solvent.
- Chromatography: Separates mixture components based on their differing affinities for a stationary phase versus a mobile phase.
- Magnetic Separation: Separates magnetic materials from non-magnetic components.
Measurement & Significant Figures Rules:
- Identifying Significant Digits:
- All non-zero digits are significant.
- Zeros positioned between non-zero digits are significant (e.g., $101$ contains $3$ significant figures).
- Leading zeros preceding non-zero digits are NOT significant (e.g., $0.001$ contains $1$ significant figure).
- Trailing zeros following a decimal point are significant (e.g., $1.00$ contains $3$ significant figures).
- Trailing zeros in a whole number without an explicit decimal point are ambiguous (e.g., $100$ has an ambiguous number of significant figures).
- Operational Rules for Calculations:
- Addition and Subtraction: The calculated result must be rounded to match the least number of decimal places present in any of the starting numbers (e.g., $1.2 + 0.34 = 1.54 \rightarrow 1.5$ ).
- Multiplication and Division: The calculated result must be rounded to match the fewest total significant figures present in any of the starting measurement values (e.g., $2.0 \times 1.234 = 2.468 \rightarrow 2.5$ ).
Metric Prefixes & Unit Conversions:
- Metric Scale Factors:
- Kilo ( $k$ ) = $10^3$
- Centi ( $c$ ) = $10^{-2}$
- Milli ( $m$ ) = $10^{-3}$
- Micro ( $\mu$ ) = $10^{-6}$
- Nano ( $n$ ) = $10^{-9}$
- Standard Conversion Factors:
- $1\,\text{inch} = 2.54\,\text{cm}$
- $1\,\text{pound} = 453.6\,\text{g}$
- $1\,\text{liter} = 1000\,\text{mL}$
- $1\,\text{gram} = 1000\,\text{mg}$
Density:
- Formula: $\text{Density} = \frac{\text{mass}}{\text{volume}}$
- Classification: Intensive property (independent of the amount of substance present).
- Standard Benchmark: Liquid water has a density of $1.0\,\text{g\,mL}^{-1}$ .

Chapter 2: Atoms, Ions, and Molecules

Subatomic Structure:
- Nucleus: Extremely small, dense, positively charged core containing protons and neutrons.
- Electrons ( $e^-$ ): Negatively charged particles orbiting the nucleus; account for virtually all of the atom's volume.
- Protons ( $p^+$ ): Positively charged subatomic particles that define elemental identity via the atomic number ( $Z$ ).
- Neutrons ( $n^0$ ): Neutral subatomic particles that add to mass without changing elemental identity.
- Mass Number ( $A$ ): Total number of protons plus neutrons ( $A = Z + n^0$ ).
Isotopes:
- Same element (same $Z$ , same proton count) with different mass numbers due to differing neutron counts.
- Chemical properties are nearly identical, while physical properties differ slightly (e.g., $^{12}\text{C}$ vs. $^{14}\text{C}$ ).
Ions:
- Cations: Positively charged ions formed by losing electrons.
- Anions: Negatively charged ions formed by gaining electrons.
- Charge Formula: $\text{Charge} = \text{protons} - \text{electrons}$ .
Key Terminology:
- Atomic Number ( $Z$ ): Number of protons; defines the element.
- Mass Number ( $A$ ): Total protons plus neutrons.
- Neutron Count: Calculated as A - Z$.
- Nuclide Notation: Written as ^{A}{Z}\text{X} $(e.g.,$ ^{14}{6}\text{C} $).</li></ul></li><li>Chemical Formulas:<ul><li>Molecular Formula: Shows the actual number of each atom (e.g.,$ \text{C}6\text{H}{12}\text{O}_6 $).</li><li>Empirical Formula: Shows the simplest whole-number ratio (e.g.,$ \text{CH}_2\text{O} $).</li><li>Structural Formula: Displays atom connectivity.</li><li>Isomers: Same molecular formula, different structural arrangements.</li></ul></li><li>Mole Concept:<ul><li>Mole ($ \text{mol} $):$ 6.022 \times 10^{23} $particles (Avogadro's number).</li><li>Molar Mass: Mass in grams of$ 1\,\text{mole} $(numerically equal to atomic or molecular mass in$ \text{u} $).</li><li>Conversions:</li><li>Grams to Moles: Divide by molar mass.</li><li>Moles to Particles: Multiply by$ 6.022 \times 10^{23} $.</li></ul></li><li>Average Atomic Mass:<ul><li>Weighted average calculated as$ \text{Average Mass} = \sum (\text{fractional abundance} \times \text{isotope mass}).

Chapter 3: Electronic Structure and Periodic Trends

Electromagnetic Radiation & Light:
- Wavelength (\lambda $): Distance between wave crests.</li><li>Frequency ($ \nu $): Number of waves per second ($ \text{Hz} $).</li><li>Wave Relationship:$ c = \lambda \nu $(higher frequency corresponds to shorter wavelength).</li><li>Photon Energy:$ E = h\nu = \frac{hc}{\lambda} (higher frequency corresponds to higher energy).
Bohr Model & Hydrogen Atom:
- Electrons occupy quantized orbits (n = 1, 2, 3, \dots $).</li><li>Ground State:$ n = 1 $(most stable).</li><li>Excited State:$ n > 1$.
- Energy difference emitted/absorbed: $\frac{1}{\lambda} = RH \left( \frac{1}{nf^2} - \frac{1}{n_i^2} \right)$ .
- Emission Series: Lyman (transitions to $n=1$ ), Balmer (transitions to $n=2$ ), Paschen (transitions to $n=3$ ).
Quantum Numbers:
- Principal ( $n$ ): Energy level ( $n = 1, 2, 3, \dots$ ).
- Angular Momentum ( $l$ ): Orbital shape ( $l = 0 \rightarrow s$ , $l = 1 \rightarrow p$ , $l = 2 \rightarrow d$ , $l = 3 \rightarrow f$ ).
- Magnetic ( $ml$ ): Orbital orientation ( $ml = -l \dots +l$ ).
- Spin ( $ms$ ): Electron spin ( $ms = +\frac{1}{2}$ or $-\frac{1}{2}$ ).
Key Quantum Rules:
- Pauli Exclusion Principle: No two electrons can share all four quantum numbers (max $2$ electrons per orbital with opposite spins).
- Hund's Rule: Electrons occupy degenerate orbitals singly with parallel spins before pairing.
Electron Configurations:
- Aufbau Order: $1s \rightarrow 2s \rightarrow 2p \rightarrow 3s \rightarrow 3p \rightarrow 4s \rightarrow 3d \rightarrow 4p \rightarrow 5s \rightarrow 4d \rightarrow 5p \rightarrow 6s \rightarrow 4f \rightarrow 5d \rightarrow 6p \rightarrow 7s$ .
- Ion Configurations: Remove electrons from highest $n$ first, then highest l$.
Periodic Trends (Driven by Effective Nuclear Charge, Z_{\text{eff}} $):<ul><li>Atomic Size: Decreases across a period, increases down a group.</li><li>Ionic Size: Cations are smaller than neutral parent atoms; anions are larger.</li><li>Ionization Energy (IE): Increases across a period, decreases down a group (exceptions at half-filled/filled subshells, e.g.,$ \text{N} > \text{O} $,$ \text{Be} > \text{B}$$).
Electron Affinity (EA): Generally increases across a period; halogens have the highest EA.

Photoelectron Spectroscopy (PES):

X-axis: Binding energy (ionization energy).
Y-axis: Relative number of electrons at that binding energy.