Atoms and the Periodic Table

Vocabulary flashcards covering the historical development of atomic models, subatomic particle properties, electron configuration, isotopic notation, and periodic table organization.

Dalton's Atomic Model

An atomic model stating that all matter consists of tiny, indivisible particles called atoms; atoms of the same element are alike, atoms of different elements vary in size and mass, and atoms can combine to form compounds.

Plum Pudding Model

Sir J.J. Thomson's atomic model proposing that an atom is a spherical cloud of positive charge with negatively charged electrons embedded throughout like fruit in a pudding.

Rutherford's Gold Foil Experiment

An experiment where positively charged alpha particles were fired at thin sheets of gold foil; because most passed straight through and only a few deflected, it demonstrated that an atom consists mostly of empty space with a tiny, dense, positively charged nucleus.

Bohr Atomic Model

An atomic model proposed by Niels Bohr stating that electrons travel around the nucleus in fixed paths or energy levels, and can jump between levels by gaining or losing discrete packets of energy.

Schrödinger Atomic Model

A 1926 quantum model using mathematical equations to describe electron shells as regions or probability clouds around the nucleus where electrons are likely to be found, rather than simple circular orbits.

Sub-atomic Particle

Any particle smaller than an atom, including protons, neutrons, and electrons.

Proton

A positively charged sub-atomic particle located inside the atomic nucleus, possessing a relative charge of $+1$, a relative mass of $1$, and represented by the symbol $p$.

Neutron

An electrically neutral sub-atomic particle located in the nucleus with a relative charge of $0$, a relative mass of $1$, and represented by the symbol $n$.

Electron

A negatively charged sub-atomic particle that orbits the nucleus, possessing a relative charge of $-1$, a relative mass of $0.0005$, and represented by the symbol $e^-$.

Valence Shell

The outermost occupied electron shell of an atom.

Valence Electrons

The electrons located within the outermost shell (valence shell) of an atom.

Atomic Number ($Z$)

The number of protons in the nucleus of an atom, which is equal to the number of electrons in a neutral atom.

Mass Number ($A$)

The total count of protons and neutrons located inside an atom's nucleus, expressed as a whole number.

Maximum Electron Shell Capacity Formula

The mathematical formula $\text{Total electrons} = 2n^2$, where $n$ is the shell number, defining the maximum quantity of electrons that a given shell can hold.

Electron Shell Filling Rule (First 20 Elements)

The stable sequence by which electrons fill inner to outer shells for the first 20 elements: up to $2$ in the first shell, $8$ in the second shell, $8$ in the third shell, and $2$ in the fourth shell.

Isotopes

Atoms of the same element that have the identical number of protons (same atomic number) but differing numbers of neutrons, resulting in different mass numbers and physical properties.

Atomic Mass

The weighted average of the mass numbers of all naturally occurring isotopes of an element, calculated using their natural relative abundances.

Group (Periodic Table)

A vertical column of elements in the periodic table; elements within the same group possess the same number of valence electrons.

Period (Periodic Table)

A horizontal row of elements in the periodic table; elements within the same period share the same valence shell level.