Chemistry: History and Development of Atomic Models

Comprehensive practice flashcards covering the historical evolution of atomic theory, subatomic particles, atomic properties, Bohr's model, and quantum concepts based on the lecture notes.

Atomos (Democritus)

The philosophical concept that matter is composed of extremely small, indivisible particles that serve as the fundamental building blocks of all bodies.

Dalton's Atomic Model

A model describing atoms as solid, indivisible spheres; atoms of the same element share the exact same mass and radius, whereas atoms of different elements differ.

Conservation of Mass (Dalton)

The principle stating that atoms cannot be created or destroyed, but can only be rearranged to form new chemical substances.

Cathode Ray Tube (Thomson)

A glass tube containing almost no air and two metal electrodes (a negative cathode and a positive anode) through which electrical rays pass under high voltage.

Cathode Rays

Streams of negatively charged particles emitted from the cathode under high voltage that bend toward the positive plate in an electric field regardless of the gas or metal used.

Thomson's Atomic Model

A model proving the atom is divisible, conceptualized as a solid, positively charged sphere with negatively charged electrons embedded on the outside.

Rutherford's Gold Foil Experiment

An experiment firing positively charged $\alpha$-particles at an ultra-thin sheet of gold foil, showing that most particles passed straight through, a small number deflected, and a tiny fraction bounced back.

Rutherford's Atomic Model

A model showing that an atom is predominantly empty space, containing a tiny, positively charged nucleus surrounded by a negatively charged electron cloud that is approximately $100\,000 \times$ larger.

Nucleons

The collective term for the subatomic particles located within the nucleus, specifically protons and neutrons.

James Chadwick's Discovery

The scientific discovery of the existence of neutral, uncharged subatomic particles called neutrons ($n^0$) residing in the atomic nucleus.

Proton ($p^+$)

A subatomic particle in the nucleus ($\approx 10^{-15}\,\text{m}$) with a mass of $1.673 \times 10^{-27}\,\text{kg}$, a relative mass of $1$, a charge of $1.60 \times 10^{-19}\,\text{C}$, and a relative charge of $+1$.

Neutron ($n^0$)

A subatomic particle in the nucleus ($\approx 10^{-15}\,\text{m}$) with a mass of $1.675 \times 10^{-27}\,\text{kg}$, a relative mass of $1$, a charge of $0\,\text{C}$, and a relative charge of $0$.

Electron ($e^-$)

A subatomic particle in the electron cloud ($\approx 10^{-10}\,\text{m}$) with a mass of $9.109 \times 10^{-31}\,\text{kg}$, a charge of $-1.60 \times 10^{-19}\,\text{C}$, and a relative charge of $-1$.

Atomic Number ($Z$)

The number of protons ($p^+$) in an atom's nucleus, which determines the element's position on the periodic table and equals the number of electrons ($e^-$) in a neutral atom.

Mass Number ($A$)

The total number of nucleons in an atom, calculated by adding the number of protons and neutrons ($\#p^+ + \#n^0$).

Isotopes

Atoms belonging to the same chemical element that have the same atomic number ($Z$), identical numbers of protons and electrons, but a different number of neutrons ($n^0$) in the nucleus.

Atomic Mass Unit ($u$)

A unit of mass defined as $\frac{1}{12}$ of the mass of a carbon-12 atom ($^{12}\text{C}$), equivalent to $1.66054 \times 10^{-27}\,\text{kg}$.

Relative Atomic Mass ($A_r$)

The dimensionless ratio of an element's absolute atomic mass to the standard atomic mass unit ($u$), having no unit of measurement.

Bohr's Atomic Model

An improved atomic model featuring $7$ main energy levels where electrons move around the nucleus along specific circular orbits with fixed radii.

Maximum Shell Capacity Formula ($2n^2$)

The mathematical rule specifying the maximum number of electrons on an energy level $n$, yielding $K=2$, $L=8$, $M=18$, and $N=32$.

Electron Configuration

The distribution and arrangement of an atom's electrons across its various concentric energy shells.

Ground State (Grondtoestand)

The lowest and most stable energy state of an atom in which all electrons occupy the lowest possible energy levels available.

Excited State (Aangeslagen Toestand)

An unstable energy state where one or more electrons absorb energy and jump to higher energy levels while lower energy positions remain vacant.

Quantum

The smallest discrete quantity of energy that an atom can absorb or emit.

Planck's Constant ($h$)

The physical constant linking photon energy to frequency in the equation $E = h \cdot \nu$, possessing a value of $6.626 \times 10^{-34}\,\text{J}\cdot\text{s}$.

Photon

A discrete quantum packet of electromagnetic energy exhibiting particle-like behavior in visible light and radiation.

Dual Nature of Electromagnetic Radiation

The property of electromagnetic radiation behaving both as a wave with frequency and wavelength, and as particles composed of discrete energy quanta (photons).

Dual Nature of the Electron

The physical characteristic whereby electrons exhibit both particle and wave properties.

Zeeman Effect (Sommerfeld Explanation)

The phenomenon where spectral lines of elements split into multiple closely spaced lines, which Sommerfeld incorporated to explain the limitations of Bohr's hydrogen-only model.