General Chemistry: Atoms, Molecules, Atomic Spectra, and Quantum Structure

Flashcards covering fundamental general chemistry concepts from Lectures 1 and 2, including atomic structure, matter classification, properties, units, electromagnetic radiation, Bohr model, atomic spectra, quantum numbers, and electron configurations.

Intensive property

A physical or chemical property that characterizes a pure substance and is independent of the amount of substance in a sample, such as density or melting point.

Extensive property

A property of a substance that depends on the quantity of matter present in a sample, such as mass, volume, length, or width.

Physical property

A characteristic of a substance that can be observed or measured without changing the chemical composition of the substance.

Chemical property

A characteristic of a substance that describes its ability to undergo a change that alters its chemical composition.

Atom

The smallest particle of an element that cannot be chemically or mechanically divided into smaller particles.

Element

A pure substance that cannot be separated into simpler substances by chemical or mechanical means, consisting entirely of atoms of the same type.

Molecule

A neutral substance containing a defined combination of atoms bonded together in a specific configuration.

Molecular formula

A symbolic representation showing the exact types and numbers of atoms bonded together in a particular molecule, such as $\text{C}_3\text{H}_6\text{O}$.

Empirical formula

A symbolic representation showing the types of atoms and the simplest whole-number ratio of atoms present in a compound.

Classification of Matter

The categorization of all matter into pure substances (elements and compounds) or mixtures (homogeneous and heterogeneous) based on physical and chemical separability.

Homogeneous mixture

A mixture that is uniform in composition throughout, such as vinegar.

Heterogeneous mixture

A mixture that is not uniform in composition throughout, such as salad dressing.

Sublimation

The phase transformation of a substance directly from the solid phase to the gas phase without passing through the liquid phase.

Deposition

The phase transformation of a substance directly from the gas phase to the solid phase without passing through the liquid phase.

Distillation

A physical separation technique used to separate miscible liquids based on differences in their boiling points.

Law of Conservation of Energy

A law stating that energy can be converted from one form into another, but cannot be created or destroyed, keeping the total energy content of the universe constant.

Precision vs. Accuracy

Precision describes the repeatability or agreement among measured values, whereas accuracy describes how close a measured value is to the true or accepted value.

Significant figures

All the digits in a measured quantity that are known with certainty plus one final estimated or uncertain digit.

Percentage error

A measure of accuracy calculated using the equation $\% \, \text{error} = \frac{|\text{measured value} - \text{accepted value}|}{\text{accepted value}} \times 100$.

Dimensional analysis

A problem-solving technique using unit conversion factors structured as $\text{value in original units} \times \text{conversion factor} = \text{value in new units}$.

Unified atomic mass unit ($u$)

A unit of mass defined as exactly $\frac{1}{12}$ of the mass of a single neutral $^{12}\text{C}$ atom.

Atomic number ($Z$)

The number of protons present in the nucleus of an atom, which uniquely defines the identity of a chemical element.

Isotopes

Atoms of the same element that share the same atomic number ($Z$) but have different numbers of neutrons and different mass numbers ($A$).

Alkali metals

The group of metallic elements found in Group 1 of the periodic table.

Alkaline earth metals

The group of metallic elements found in Group 2 of the periodic table.

Chalcogens

The group of nonmetallic and metalloid elements found in Group 16 of the periodic table.

Halogens

The group of highly reactive nonmetallic elements found in Group 17 of the periodic table.

Noble gases

The group of unreactive nonmetallic gaseous elements found in Group 18 of the periodic table.

Average atomic mass

The weighted average mass of an element's naturally occurring isotopes, calculated as $\text{Average atomic mass} = a_1 m_1 + a_2 m_2 + \dots + a_n m_n$, where $a_x$ represents fractional natural abundance and $m_x$ represents isotopic mass.

Mole

The SI base unit for amount of substance, containing Avogadro's number ($6.022 \times 10^{23}\,mol^{-1}$) of particles, defined as the number of atoms in exactly $12\,g$ of $^{12}\text{C}$.

Molar mass

The mass of one mole of a chemical substance expressed in $g\,mol^{-1}$, calculated as the sum of the average atomic masses of all atoms in its chemical formula.

Speed of light ($c$)

A fundamental physical constant representing the speed of electromagnetic radiation in a vacuum, equal to $2.998 \times 10^8\,m\,s^{-1}$.

Planck's constant ($h$)

A fundamental constant relating the energy of a photon to its electromagnetic frequency, equal to $6.626 \times 10^{-34}\,J\,s$.

Photon energy formula

The mathematical relationship giving the discrete energy of a photon: $E = h\nu$ or $E = \frac{hc}{\lambda}$.

Photoelectric effect

The phenomenon in which electrons are emitted from a metal surface when light of at least a threshold frequency shines on the metal.

Rutherford model of the atom

An atomic model established through alpha-particle scattering experiments showing that an atom is mostly empty space with its positive charge and mass concentrated in a central nucleus.

Bohr model of the atom

An atomic model proposing that electrons move in specific, quantized circular orbits around the nucleus without radiating energy.

Rydberg equation

An equation calculating the wavelengths of light emitted or absorbed during electron transitions in hydrogen: $\frac{1}{\lambda} = R_H \left(\frac{1}{n_f^2} - \frac{1}{n_i^2}\right)$, where $R_H = 1.0974 \times 10^7\,m^{-1}$.

Spectral Series of Hydrogen

Quantized electron transitions in hydrogen categorized into series based on the final principal quantum level: Lyman ($n_f = 1$, ultraviolet), Balmer ($n_f = 2$, visible), and Paschen ($n_f = 3$, infrared).

Bohr transition energy formula

The formula calculating the energy change during an electron transition in hydrogen: $\Delta E = R_Y \left(\frac{1}{n_f^2} - \frac{1}{n_i^2}\right)$, where $R_Y = -2.178 \times 10^{-18}\,J$.

Principal quantum number ($n$)

The quantum number ($n = 1, 2, 3 \dots$) that defines the main energy level, electron shell, and overall size of an atomic orbital.

Angular momentum quantum number ($l$)

The quantum number ($l = 0, 1 \dots n-1$) that defines the subshell and three-dimensional shape of an atomic orbital ($s, p, d, f$).

Magnetic quantum number ($m_l$)

The quantum number ($m_l = 0, \pm 1 \dots \pm l$) defining the spatial orientation of an atomic orbital around the nucleus.

Spin quantum number ($m_s$)

The quantum number describing the intrinsic spin direction of an electron in an orbital, taking values of $m_s = +\frac{1}{2}$ (spin up) or $m_s = -\frac{1}{2}$ (spin down).

Pauli exclusion principle

The principle stating that no two electrons in an atom can have the same four quantum numbers ($n, l, m_l, m_s$), meaning an orbital can hold a maximum of two electrons with opposing spins.

Aufbau principle

The rule stating that electrons fill lower-energy atomic orbitals before occupying higher-energy orbitals.

Hund's rule

The rule stating that for degenerate orbitals, the most stable electron configuration maximizes the number of electrons with parallel spins by placing one electron in each orbital before pairing.

Paramagnetic

Refers to an atom or ion that possesses one or more unpaired electrons, causing it to be attracted to an external magnetic field.

Diamagnetic

Refers to an atom or ion in which all electrons are paired, causing it to be weakly repelled by an external magnetic field.

Madelung Series

The sequence determining the order in which atomic subshells are filled with electrons based on increasing $(n + l)$ energy levels.

Isoelectronic species

Atoms, cations, or anions that possess identical total numbers of electrons and the exact same ground-state electron configuration.