Comprehensive Chemistry Review: Atomic Theory, States of Matter, Bonding, Reactions, and Stoichiometry

Comprehensive practice flashcards reviewing all key concepts from the chemistry lectures, including atomic models, subatomic particles, periodic properties, phase thermodynamics, states of matter, chemical bonding, reaction classes, gas laws, and stoichiometric yield calculations.

Who was the first philosopher to propose the concept of atoms, and who later provided the first scientific atomic theory?

Democritus was the first to propose the idea of atoms, and John Dalton provided the first scientific theory of the atom based on the work of Joseph Proust.

What is Joseph Proust's law of definite proportions?

It states that each chemical compound contains the exact same proportion of elements by mass.

What were the four core postulates of Dalton's Atomic Theory?

1. Atoms are indivisible and cannot be broken down.
2. Elements are composed of identical atoms that are unique to each element.
3. Compounds are composed of atoms of two or more elements combined in fixed proportions.
4. A chemical reaction is a rearrangement of atoms into new combinations; it cannot create or destroy atoms.

How did J.J. Thomson modify Dalton's model of the atom through his cathode ray experiments?

Thomson discovered that cathode rays consist of negatively charged particles (electrons) and proposed the Plum Pudding Model, in which electrons float in a sea of positive charge, maintaining overall electrical neutrality.

What did Robert Millikan's oil drop experiment determine about the electron?

Millikan measured the rate of fall of charged oil droplets to determine the charge of an electron, which, when combined with Thomson's mass-to-charge ratio, allowed the determination of both the mass and charge of the electron.

What were the experimental observations and key conclusions of Ernest Rutherford's gold foil experiment?

Observations: Most positively charged particles passed straight through the thin gold foil, while a few were deflected at very large angles. Conclusions: An atom is mostly empty space with its positive charge and mass concentrated in a tiny central volume called the nucleus.

How did Heinrich Hertz and Albert Einstein contribute to the modern understanding of the photoelectric effect?

Hertz (1887) observed that shining light on metal produces electron emissions whose energy depends on frequency, not intensity. Einstein explained this by proposing light behaves as quantized particles (photons) with energy given by $E = h\nu$.

What atomic model did Niels Bohr propose in 1915?

Bohr proposed the planetary model, asserting that electrons orbit the nucleus in discrete paths or energy levels ($n = 1, 2, 3, 4$).

What are the masses (in grams and amu) and charges of the three subatomic particles?

Proton: charge $+1$, mass $1.673 \times 10^{-24}\,\text{g}$ ($\approx 1\,\text{amu}$). Neutron: charge $0$, mass $1.675 \times 10^{-24}\,\text{g}$ ($\approx 1\,\text{amu}$). Electron: charge $-1$, mass $9.109 \times 10^{-28}\,\text{g}$ ($\approx 0.0006\,\text{amu}$).

What is the difference between atomic number ($Z$) and mass number ($A$)?

The atomic number ($Z$) is the number of protons in an atom's nucleus and identifies the element. The mass number ($A$) is the total number of protons and neutrons in the nucleus.

What is an isotope, and what formula is used to calculate the average atomic mass ($M_A$)?

Isotopes are atoms of the same element with identical numbers of protons and electrons but different numbers of neutrons. The formula is: $M_A = (M_1)(P_1) + (M_2)(P_2) + \dots + (M_n)(P_n)$ where $M$ represents the isotopic mass and $P$ represents the fractional abundance.

How do homogeneous mixtures differ from heterogeneous mixtures, and what are two common physical separation methods?

Homogeneous mixtures appear uniform as a single phase (e.g., salt water), while heterogeneous mixtures consist of distinguishable components (e.g., soil). They can be separated by physical methods such as distillation (based on boiling point differences) and chromatography (based on migration through a substrate).

What are the four quantum numbers and the maximum electron capacity of an electron shell?

The quantum numbers are $n$ (principal), $l$ (angular momentum, values $0$ to $n-1$), $m$ (magnetic, values $-l$ to $+l$), and $m_s$ (spin, values $+\frac{1}{2}$ or $-\frac{1}{2}$). The maximum number of orbitals in a shell is $n^2$, and the maximum electron capacity is $2n^2$.

State the Pauli exclusion principle, Hund's rule, and the Aufbau principle.

Pauli Exclusion Principle: No two electrons in an atom can have identical sets of quantum numbers. Hund's Rule: Electrons occupy degenerate orbitals singly with parallel spins before pairing up. Aufbau Principle: Electrons fill orbitals in order of increasing energy levels from lowest to highest.

How did Antoine Lavoisier, John Newlands, Dmitri Mendeleev, and Henry Moseley contribute to the periodic table?

Lavoisier (1789) categorized substances as acid-making, gas-like, metallic, or earthy. Newlands (1865) formulated the law of octaves by atomic mass. Mendeleev (1869) arranged elements by atomic mass and left blank spaces for undiscovered elements. Moseley (1909) organized the modern periodic table by increasing atomic number.

What are the defining characteristics of alkali metals, alkaline earth metals, halogens, and noble gases?

Alkali Metals (Group 1): Soft, silver, highly reactive with water/oxygen, form $+1$ cations. Alkaline Earth Metals (Group 2): Low density, form $+2$ cations. Halogens (Group 17): Reactive nonmetals, exist as diatomic molecules, form $-1$ anions. Noble Gases (Group 18): Nonreactive, odorless, tasteless, low boiling points.

What are the periodic trends for atomic radius across a period and down a group?

Atomic radius decreases from left to right across a period (due to increasing nuclear charge pulling the same energy level closer) and increases down a group (due to electrons being added to higher principal energy levels).

Why is the first ionization energy of Group 13 elements lower than that of Group 2 elements?

The outermost electron in Group 13 occupies a $p$ orbital, which is shielded from the full nuclear pull by the completed inner $s$ subshell, making that electron easier to remove.

Why is the first ionization energy of Group 16 elements lower than that of Group 15 elements?

Group 15 elements have a stable half-filled $p^3$ subshell, whereas Group 16 elements have a $p^4$ configuration where two electrons must pair up in an orbital, causing electron-electron repulsion that makes removal easier.

What are the primary postulates of the Kinetic-Molecular Theory (KMT) for ideal gases?

1. Gases consist of large numbers of tiny, hard spherical particles in constant, random motion.
2. Most of the volume of a gas is empty space (particle volume is negligible).
3. There are no attractive or repulsive intermolecular forces between gas particles.
4. Collisions between particles and with container walls are perfectly elastic.
5. Average kinetic energy is directly proportional to absolute temperature.

What is Graham's law regarding gas effusion?

Graham's law states that the rate of effusion of a gas is inversely proportional to the square root of its molar mass ($\text{rate} \propto \frac{1}{\sqrt{M}}$), meaning lighter gas molecules effuse faster than heavier ones.

What is viscosity, and how is it related to temperature, molecular mass, and intermolecular forces?

Viscosity is the resistance of a liquid to flow. It is inversely proportional to temperature (higher temperature lowers viscosity) and directly proportional to both molecular mass and the strength of intermolecular forces.

What structural feature distinguishes crystalline solids from amorphous solids?

Crystalline solids possess long-range order with a repeating, periodic three-dimensional lattice made of unit cells. Amorphous solids lack long-range order because rapid cooling prevents complete assembly, resulting in a nonuniform particle arrangement.

What is plasma, and what conditions allow cold (non-thermal) plasmas to exist?

Plasma is a high-energy state of matter composed of free electrons and cations that conducts electricity and has no fixed shape or volume. Non-thermal plasmas occur when fast, light electrons are hot while heavy nuclei remain slow and cold, with fewer than $1\%$ of particles ionized.

What are the six phase transitions between solids, liquids, and gases?

Melting: Solid to liquid Freezing: Liquid to solid Boiling/Evaporation: Liquid to vapor Condensing: Vapor to liquid Sublimation: Solid directly to vapor Deposition: Vapor directly to solid

What happens to the temperature of a pure substance during a phase change?

The temperature remains constant during a phase change because the added or removed thermal energy is used to break or form intermolecular attractions rather than altering the average kinetic energy.

What is vapor pressure, and how is it affected by temperature?

Vapor pressure is the pressure exerted by a gas in thermodynamic equilibrium with its liquid phase in a closed system at a given temperature; it increases directly with increasing temperature.

How do intensive properties differ from extensive properties of matter?

Intensive properties depend only on the identity of the substance and not on sample size (e.g., density, melting point, conductivity, magnetism). Extensive properties depend directly on the amount of substance present (e.g., mass, volume, length).

What are the common visual and physical indicators that a chemical reaction has taken place?

Precipitate (solid) formation, gas formation (bubbling), unexpected color change, temperature change (heat absorption/release), and light emission.

What is an ionic bond, and what difference in electronegativity typically characterizes it?

An ionic bond is the electrostatic attraction between oppositely charged ions formed by the complete transfer of valence electrons from a metal (cation) to a nonmetal (anion), occurring when the electronegativity difference is greater than $1.7$.

What is lattice energy, and what factors increase its magnitude?

Lattice energy is the energy released when gaseous ions combine to form one mole of an ionic crystalline solid. Its magnitude increases with smaller ionic radii and higher ionic charges.

What is the difference between a sigma ($\sigma$) bond and a pi ($\pi$) bond in covalent molecules?

A sigma bond results from the direct, head-on overlap of $s, p$, or $d$ orbitals along the internuclear axis (allowing the sharing of two electrons). A pi bond results from the parallel, sideways overlap of unhybridized $p$ orbitals above and below the internuclear axis.

What constitutes a double bond and a triple bond in terms of orbital overlap?

A double bond consists of one sigma ($\sigma$) bond and one pi ($\pi$) bond. A triple bond consists of one sigma ($\sigma$) bond and two pi ($\pi$) bonds oriented at $90^\circ$ to each other.

What electronegativity difference ranges define nonpolar covalent and polar covalent bonds?

Nonpolar covalent bonds exhibit equal sharing with an electronegativity difference of $\le 0.4$. Polar covalent bonds exhibit unequal sharing and partial charges with an electronegativity difference of $\ge 0.5$.

What is an expanded octet in Lewis structure theory?

An expanded octet is a condition in certain central nonmetal atoms (period 3 and below) that utilize vacant, low-lying $d$ orbitals to accommodate more than eight valence electrons during bonding.

What general physical properties distinguish covalent compounds from ionic compounds?

Covalent compounds consist of neutral molecules with weak intermolecular forces, resulting in low melting/boiling points, poor electrical and thermal conductivity, and lack of ionization in solution. Ionic compounds form rigid crystalline lattices with high melting points and conduct electricity when molten or aqueous.

What are the five primary classifications of chemical reactions?

1. Synthesis: $A + B \rightarrow AB$
2. Decomposition: $AB \rightarrow A + B$
3. Combustion: $A + \text{O}_2 \rightarrow \text{oxide of } A$
4. Single Replacement: $A + BC \rightarrow AC + B$
5. Double Replacement: $AB + CD \rightarrow AD + CB$

How does the activity series predict whether a single-replacement reaction will occur?

A single-replacement reaction will proceed spontaneously only if the lone reacting element is higher (more reactive and less stable in elemental form) on the activity series than the element it seeks to replace in the compound.

State Boyle's law and provide its mathematical expression.

Boyle's law states that the pressure and volume of a fixed mass of gas are inversely proportional at constant temperature: $P_1V_1 = P_2V_2$ (or $PV = k$).

State Charles's law and provide its mathematical formula.

Charles's law states that the volume of a fixed quantity of gas is directly proportional to its absolute temperature in Kelvin under constant pressure: $\frac{V_1}{T_1} = \frac{V_2}{T_2}$.

State Gay-Lussac's law and explain why water boils when placed on ice in a sealed container.

Gay-Lussac's law states that gas pressure is directly proportional to absolute Kelvin temperature at constant volume (measured as $\frac{P_1}{T_1} = \frac{P_2}{T_2}$). When cooled on ice, the gas pressure above the water decreases until it equals the water's vapor pressure, causing it to boil.

What is the combined gas law formula, and what relationship does it describe?

The formula is: $\frac{P_1V_1}{T_1} = \frac{P_2V_2}{T_2}$ It shows that for a fixed quantity of gas, pressure varies inversely with volume while absolute temperature varies directly with both pressure and volume.

What is the Joule-Thomson effect observed when an aerosol can is sprayed?

When compressed gas is rapidly released into lower atmospheric pressure, the expanding gas molecules do work to separate against attractive forces, causing their kinetic energies and the temperature of the gas to decrease.

State Dalton's law of partial pressures and the equation relating partial pressure to mole fraction.

Dalton's law states that the total pressure of a gas mixture is the sum of the partial pressures of its component gases: $P_T = P_1 + P_2 + \dots + P_n$ The partial pressure of gas $a$ is given by: $P_a = \left(\frac{n_a}{n_T}\right)P_T$.

State Avogadro's law and the volume occupied by one mole of any gas at STP ($0^\circ\text{C}$, $1.0\,\text{atm}$).

Avogadro's law states that the volume of a gas is directly proportional to the number of moles of gas at constant temperature and pressure ($\frac{V_1}{n_1} = \frac{V_2}{n_2}$). One mole of any ideal gas at STP occupies $22.4\,\text{L}$.

What is the Ideal Gas Law equation, and what are the numerical values of the gas constant $R$ in different pressure units?

The equation is $PV = nRT$. The values of $R$ are:

• $0.0821\,\text{L}\cdot\text{atm}/(\text{mol}\cdot\text{K})$
• $62.396\,\text{L}\cdot\text{torr}/(\text{mol}\cdot\text{K})$
• $8.317\,\text{L}\cdot\text{kPa}/(\text{mol}\cdot\text{K})$

Under what specific conditions do real gases deviate significantly from ideal gas behavior?

Real gases deviate from ideality under conditions of very high pressure (where particle volumes are no longer negligible relative to total volume) and very low temperature (where low kinetic energy allows intermolecular attractions to take effect).

What is stoichiometry, and what fundamental tool from a balanced chemical equation makes stoichiometric calculations possible?

Stoichiometry is the study and calculation of relative amounts of substances involved in chemical reactions, which relies on the exact mole ratios derived from coefficients in a balanced chemical equation.

What three-step conversion sequence is used to calculate the mass of a product from the mass of a reactant?

1. Convert grams of given reactant to moles of reactant using the inverse of its molar mass ($\frac{1\,\text{mol}}{M_R}$).
2. Convert moles of reactant to moles of product using the stoichiometric mole ratio ($\frac{\text{mol product}}{\text{mol reactant}}$).
3. Convert moles of product to grams of product using its molar mass ($\frac{M_P}{1\,\text{mol}}$).

How is the limiting reactant identified in a chemical reaction with known quantities of multiple reactants?

Calculate the amount of product formed from each available reactant quantity based on stoichiometric mole ratios; the reactant that yields the smallest quantity of product is the limiting reactant.

What is the difference between theoretical yield and actual yield, and how is percent yield calculated?

Theoretical yield is the calculated maximum amount of product that can form under stoichiometric conditions. Actual yield is the measured amount of product collected from an experiment. The formula is: $\%\,\text{Yield} = \frac{\text{Actual yield}}{\text{Theoretical yield}} \times 100$.