General Chemistry: Atoms, Stoichiometry, Thermochemistry, and Chemical Composition

Flashcards covering atomic structure, electromagnetic radiation, quantum electron configurations, periodic trends, reaction stoichiometry, thermochemistry, and chemical composition calculations.

Key progression from Rutherford to Bohr to Quantum atomic models

Rutherford: electrons orbit a dense nucleus. Bohr: electrons travel in quantized circular orbits ($n = 1, 2, 3\dots$). Quantum: electrons behave as waves and particles in 3D probability orbitals.

Equations relating photon energy ($E$), light speed ($c$), wavelength ($\lambda$), and frequency ($\nu$)

$c = \lambda\nu$ and $E = h\nu = \frac{hc}{\lambda}$

Why atomic emission spectra consist of discrete lines rather than a continuous spectrum

Electron energy levels are quantized, so photons are emitted only at discrete wavelengths corresponding to transitions between specific energy states.

Primary limitation of the Bohr atomic model

Accurately predicts emission spectra only for hydrogen and one-electron ions; fails for multi-electron atoms.

Shape, spatial orientation, and electron capacity of a $p_x$ orbital

Dumbbell-shaped orbital aligned along the x-axis that holds up to 2 electrons.

Shape, spatial plane, and electron capacity of a $d_{xy}$ orbital

Four-lobed cloverleaf orbital lying in the xy-plane that holds up to 2 electrons.

Orbital counts and electron capacities of $s, p, d, f$ subshells

$s$: 1 orbital (2 electrons); $p$: 3 orbitals (6 electrons); $d$: 5 orbitals (10 electrons); $f$: 7 orbitals (14 electrons).

Summary of Aufbau principle, Pauli exclusion principle, and Hund's rule

Aufbau: fill lowest-energy orbitals first. Pauli: maximum 2 electrons per orbital with opposite spins. Hund's: half-fill degenerate orbitals with parallel spins before pairing.

Ground-state anomalous electron configurations of $Cr$ and $Cu$

One $4s$ electron promotes to $3d$ to yield stable half-filled or fully filled subshells: $Cr: [Ar]\,4s^1 3d^5$ and $Cu: [Ar]\,4s^1 3d^{10}$.

Periodic trends for atomic radius and first ionization energy

Atomic radius increases down a group and decreases across a period. First ionization energy decreases down a group and increases across a period.

Meanings of the reaction state symbols $(s)$, $(l)$, $(g)$, and $(aq)$

$(s)$ solid, $(l)$ liquid, $(g)$ gas, and $(aq)$ aqueous (dissolved in water).

Definition and determination of the limiting reactant

The reactant completely consumed first that limits product formation; determined by calculating which reactant yields the fewest moles of product.

Formula for calculating percent yield

$$\text{Percent Yield} = \frac{\text{Actual yield}}{\text{Theoretical yield}} \times 100$$

Thermochemical classification of a reaction where reactants have higher potential energy than products

Exothermic ($q < 0$), releasing heat energy to the surroundings.

Energy changes during chemical bond breaking versus bond forming

Bond breaking is endothermic (requires energy, $+q$); bond forming is exothermic (releases energy, $-q$).

Classification of phase changes into endothermic versus exothermic processes

Endothermic ($+q$): melting, vaporization, and sublimation. Exothermic ($-q$): freezing, condensation, and deposition.

Dr. Reatha Clark King's scientific contribution to NASA rocket research

Accurately measured heats of formation and reaction for hypergolic chlorine trifluoride ($ClF_3$) used as a rocket fuel oxidizer.

Definition of specific heat capacity ($C$) and its heat equation

Heat needed to raise the temperature of $1\,g$ of a substance by $1\,^\circ\text{C}$; calculated via $q = m \times C \times \Delta T$.

Conversion factors among calories, dietary Calories, joules, and kilowatt-hours

$1\,\text{cal} = 4.184\,J$, $1\,\text{Cal} = 1000\,\text{cal} = 4184\,J$, and $1\,\text{kWh} = 3.60 \times 10^6\,J$.

Value and defining standard of Avogadro's number

$6.022 \times 10^{23}\,mol^{-1}$, defined as the exact number of atoms in $12\,g$ of pure carbon-12.

Distinction between formula mass and molar mass

Formula mass is the mass of one molecule or formula unit in $amu$; molar mass is the mass of one mole of units in $g\,mol^{-1}$.

Mario Molina's Nobel Prize-winning environmental discovery

Discovered that CFCs break down under solar radiation to release chlorine atoms that catalytically destroy stratospheric ozone.

Why stratospheric chlorine acts as a catalyst in ozone depletion

Chlorine radicals destroy ozone and regenerate in the reaction cycle, allowing a single radical to destroy thousands of $O_3$ molecules.

Formula for the mass percent of an element in a compound

$$\text{Mass percent of } X = \frac{\text{Mass of } X \text{ in } 1\,mol \text{ of compound}}{\text{Mass of } 1\,mol \text{ of compound}} \times 100$$

Relationship between an empirical formula and a molecular formula

Empirical formula is the simplest whole-number atom ratio; molecular formula gives actual atom counts: $\text{Molecular} = (\text{Empirical})_n$, where $n = \frac{\text{molar mass}}{\text{empirical formula mass}}$.

Distinction between valence electrons and core electrons

Valence electrons occupy the outermost shell and participate in bonding; core electrons fill inner shells and shield nuclear charge.

Rule for determining valence electrons in main-group elements (groups 1, 2, and 13–18)

Groups 1 and 2 equal the group number; groups 13 to 18 equal the group number minus 10.

Electrons counted as valence electrons in d-block transition metals

The outermost highest-energy $s$ electrons plus the highest-energy $d$ electrons.

Ground-state anomalous electron configurations of $Mo$ and $Ag$

$Mo: [Kr]\,5s^1 4d^5$ (half-filled $4d$) and $Ag: [Kr]\,5s^1 4d^{10}$ (fully filled $4d$).

Ion formation behavior of main-group metals versus nonmetals

Metals lose valence electrons to form cations isoelectronic with the preceding noble gas; nonmetals gain electrons to form anions isoelectronic with the next noble gas.

Distinction between the system and the surroundings in thermodynamics

The system is the specific chemical or physical process under study; surroundings include everything else in the universe.

Surroundings temperature change in exothermic versus endothermic processes

Exothermic releases heat to the surroundings, raising their temperature; endothermic absorbs heat from the surroundings, lowering their temperature.

Thermal consequence of water's high specific heat capacity compared to metals

Water resists temperature change significantly more, absorbing or releasing large amounts of heat with minimal temperature variation.

Balancing chemical equations: coefficients versus subscripts

Adjust only stoichiometric coefficients in front of formulas; never alter subscripts, as changing subscripts changes the chemical identity.

Distinction between theoretical yield and actual yield

Theoretical yield is the maximum product mass calculated from the limiting reactant; actual yield is the product mass experimentally isolated.

Procedure for calculating an empirical formula from percent or mass composition

Convert elemental masses to moles, divide each by the smallest mole value, and multiply by small integers if needed to obtain whole numbers.

Ground-state versus excited-state electron configuration

Ground state has electrons in the lowest possible energy orbitals; excited state has one or more electrons promoted to higher orbitals, leaving vacancies below.

Progression of atomic models (Rutherford to Bohr to Quantum)

Rutherford placed electrons orbiting a dense nucleus; Bohr placed electrons in quantized circular orbits ($n = 1, 2, 3\dots$); Quantum mechanics models electrons as waves and particles in 3D probability clouds called orbitals.

Equations relating light speed, wavelength, frequency, and photon energy

$c = \lambda\nu$ and $E = h\nu = \frac{hc}{\lambda}$

Why atomic emission spectra show discrete lines instead of a continuous rainbow

Electron energy levels are quantized, meaning electrons jump between specific energy states and release photons only at distinct wavelengths.

Main limitation of the Bohr atomic model

It accurately predicts emission spectra only for hydrogen and single-electron ions, failing for atoms with multiple electrons.

Shape, orientation, and electron capacity of a $p_x$ orbital

Dumbbell-shaped orbital aligned on the x-axis that can hold up to 2 electrons.

Shape, plane, and electron capacity of a $d_{xy}$ orbital

Four-lobed cloverleaf orbital lying in the xy-plane that can hold up to 2 electrons.

Orbital counts and electron capacities for $s, p, d, f$ subshells

$s$ has 1 orbital (2 electrons); $p$ has 3 orbitals (6 electrons); $d$ has 5 orbitals (10 electrons); $f$ has 7 orbitals (14 electrons).

Rules for filling electron orbitals (Aufbau, Pauli exclusion, Hund's rule)

Aufbau fills lowest-energy levels first; Pauli allows up to 2 electrons per orbital with opposite spins; Hund's rule places one electron in each equal-energy orbital before pairing.

Ground-state electron configurations for chromium ($Cr$) and copper ($Cu$)

An electron promotes from $4s$ to $3d$ to achieve half-filled or fully filled stability: $Cr: [Ar]\,4s^1 3d^5$ and $Cu: [Ar]\,4s^1 3d^{10}$.

Periodic trends for atomic radius and first ionization energy

Atomic radius increases going down a group and decreases across a period; ionization energy decreases going down a group and increases across a period.

Meanings of reaction state symbols: $(s)$, $(l)$, $(g)$, and $(aq)$

$(s)$ means solid, $(l)$ means liquid, $(g)$ means gas, and $(aq)$ means aqueous (dissolved in water).

Limiting reactant definition and method of identification

The reactant that gets used up first and caps the amount of product; found by calculating which reactant yields the fewest moles of product.

Formula for percent yield

$$\text{Percent Yield} = \frac{\text{Actual yield}}{\text{Theoretical yield}} \times 100$$

Classification of a reaction where reactants hold higher potential energy than products

Exothermic ($q < 0$), because extra energy is released as heat to the surroundings.

Energy changes in chemical bond breaking versus bond forming

Breaking bonds requires energy (endothermic, $+q$); making bonds releases energy (exothermic, $-q$).

Phase changes categorized into endothermic vs. exothermic

Endothermic (absorbs heat): melting, vaporization, and sublimation. Exothermic (releases heat): freezing, condensation, and deposition.

Dr. Reatha Clark King's scientific discovery for NASA rocket research

Accurately measured heats of reaction for highly reactive chlorine trifluoride ($ClF_3$) used as a rocket propellant oxidizer.

Definition and formula for specific heat capacity ($C$)

The heat required to raise the temperature of $1\,g$ of a substance by $1\,^\circ\text{C}$; calculated using $q = m \times C \times \Delta T$.

Conversion values between calories, dietary Calories, joules, and kilowatt-hours

$1\,\text{cal} = 4.184\,J$, $1\,\text{Cal} = 1000\,\text{cal} = 4184\,J$, and $1\,\text{kWh} = 3.60 \times 10^6\,J$.

Avogadro's number and its official standard

$6.022 \times 10^{23}\,mol^{-1}$, defined as the number of atoms in exactly $12\,g$ of pure carbon-12.

Formula mass vs. molar mass

Formula mass is the mass of a single molecule or formula unit measured in $amu$; molar mass is the mass of one mole ($6.022 \times 10^{23}$ units) measured in $g\,mol^{-1}$.

Mario Molina's Nobel Prize-winning environmental finding

Discovered that chlorofluorocarbons (CFCs) break down in solar radiation to release chlorine atoms that destroy Earth's protective ozone layer.

Reason stratospheric chlorine acts as a catalyst in ozone breakdown

Chlorine radicals destroy ozone and reform during the cycle, allowing one radical to break down thousands of $O_3$ molecules.

Formula for elemental mass percent in a compound

$$\text{Mass percent} = \frac{\text{Mass of element in } 1\,mol \text{ of compound}}{\text{Molar mass of compound}} \times 100$$

Empirical formula vs. molecular formula relationship

The empirical formula is the lowest whole-number atom ratio; the molecular formula gives actual atom counts via $\text{Molecular} = (\text{Empirical})_n$, where $n = \frac{\text{molar mass}}{\text{empirical formula mass}}$.

Valence electrons vs. core electrons

Valence electrons sit in the outermost shell and participate in bonding; core electrons fill inner shells and shield positive nuclear charge.

Method for finding valence electrons in main-group elements (groups 1, 2, 13–18)

For groups 1 and 2, it equals the group number; for groups 13 to 18, it equals the group number minus 10.

Which electrons count as valence electrons in d-block transition metals

The outermost highest-energy $s$ electrons plus the highest-energy $d$ electrons.

Ground-state anomalous electron configurations of $Mo$ and $Ag$

$Mo: [Kr]\,5s^1 4d^5$ (half-filled $4d$ subshell) and $Ag: [Kr]\,5s^1 4d^{10}$ (fully filled $4d$ subshell).

How main-group metals and nonmetals form ions

Metals lose valence electrons to form positive cations matching the prior noble gas; nonmetals gain electrons to form negative anions matching the next noble gas.

Thermodynamic distinction between system and surroundings

The system is the specific chemical or physical process being studied; the surroundings include everything else in the universe.

Temperature change of the surroundings in exothermic vs. endothermic reactions

Exothermic processes release heat into the surroundings to make them hotter; endothermic processes absorb heat from the surroundings to make them cooler.

Physical impact of water having a high specific heat capacity

Water strongly resists changes in temperature, absorbing or shedding large quantities of heat with only minimal changes in its own temperature.

Rule for balancing equations: coefficients vs. subscripts

Only adjust stoichiometric coefficients in front of formulas; never alter chemical subscripts, which would alter the substance's chemical identity.

Theoretical yield vs. actual yield

Theoretical yield is the maximum product mass calculated from the limiting reactant; actual yield is the amount of product physically collected in an experiment.

Steps to find an empirical formula from mass composition data

Convert mass of each element into moles, divide every mole value by the smallest calculated mole value, and multiply by small integers if needed to yield whole numbers.

Ground state vs. excited state electron configurations

A ground state places all electrons in the lowest possible energy orbitals; an excited state features one or more electrons bumped to higher energy orbitals.