Science 8: Atomic Structure, Periodic Table Development, and Electron Configurations

Comprehensive vocabulary flashcards reviewing atomic models, subatomic particles, element and compound definitions, historical development of the periodic table, periodic trends, periods, groups, subshells, and electron configurations.

Atom

The smallest unit of matter.

Nucleus

The massive center of an atom composed of protons and neutrons.

Energy Level

A fixed region around the nucleus where electrons move, denoted by the letter $n$.

Electron Cloud

The path or region where electrons are likely to be found according to the modern atomic model.

Atomic Model

A scientific representation of the structure of an atom.

Proton

A positively charged subatomic particle ($p^+$) located inside the nucleus.

Neutron

A subatomic particle ($n^0$) located inside the nucleus that carries no electrical charge.

Electron

A negatively charged subatomic particle ($e^-$) found outside the nucleus.

Atomism

The philosophical concept proposed by Democritus in 400 BC stating that matter is composed of tiny, indivisible particles called atomos.

Solid Sphere Model

The atomic model proposed by John Dalton in 1803 stating that all matter is made of solid, indivisible spherical atoms.

Plum Pudding Model

The atomic model proposed by J.J. Thomson in 1897 suggesting the atom is a sphere containing negative charges (electrons), based on experiments with cathode rays.

Nuclear Model

The atomic model developed by Ernest Rutherford in 1911 from the gold foil experiment, demonstrating that most of the atom is empty space and the positive charge is concentrated in a tiny nucleus.

Planetary Model

The atomic model proposed by Niels Bohr in 1913 stating that electrons travel around the nucleus in fixed energy levels and can jump between levels by gaining or losing energy.

Modern Atomic Model

The quantum mechanical model formulated by Erwin Schrödinger in 1926 proposing that electrons do not move in fixed paths but reside in regions of probability called electron clouds.

Atomic Number (AN)

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

Atomic Mass (AM)

The total mass of an atom, calculated by adding protons and neutrons ($\text{Proton} + \text{Neutron}$).

Octet Rule

The rule stating that atoms tend to become more stable when their outermost electron shell contains $8$ electrons.

2-8-8 Rule

The electron distribution rule followed by the first $20$ elements in the periodic table, where shells hold a maximum of $2$, $8$, and $8$ electrons successively.

Pure Substance

A homogeneous form of matter with a uniform, definite composition throughout that cannot be separated into simpler substances by physical means.

Mixture

Matter that does not have a constant chemical composition or uniform properties throughout, failing the criteria of a pure substance.

Element

A pure substance made up of only one type of atom with identical atomic numbers, which cannot be broken down into simpler substances by chemical means and is represented by chemical symbols.

Compound

A pure substance composed of different elements chemically combined in a fixed ratio, which can be separated by chemical means and is represented by chemical formulas.

Triads of Elements

A system proposed by Johann Wolfgang Döbereiner (1790-1849) classifying elements into groups of $3$ with similar properties, showing the first mathematical relationship between atomic weight and chemical traits.

Telluric Helix

A spiral arrangement developed by Alexandre-Émile Béguyer de Chancourtois (1820-1886) arranging elements by atomic weight on a 16-unit cylinder to demonstrate repeating periodic properties.

Law of Octaves

A classification proposed by John Newlands (1887-1898) stating that every $8$ elements arranged in increasing atomic mass share similar properties, which held true only up to calcium.

Periodic Law (Mendeleev)

The principle formulated by Dmitri Mendeleev (1834-1907) asserting that elements exhibit periodic patterns in their properties when ordered by increasing atomic mass.

Modern Periodic Law (Moseley)

The ordering concept introduced by Henry Moseley (1887-1915) arranging elements by increasing atomic number instead of atomic mass/weight, resolving Mendeleev's ordering anomalies.

Actinides

An additional series of elements proposed by Glenn T. Seaborg (1912-1999) that restructured the periodic table to better reflect electron configurations and chemical traits.

Periodic Table of Elements

A chart showcasing periodic patterns of elements organized in rows and columns based on increasing atomic number, electron configuration, and chemical properties.

Periods

The $7$ horizontal rows of the periodic table, numbered from left to right, corresponding to the principal energy level ($n$) occupied by an element's outermost electrons.

Groups

The $18$ vertical columns of the periodic table, numbered from top to bottom, containing elements with identical numbers of valence electrons.

Naturally Occurring Elements

The $94$ elements out of the $118$ known elements that occur naturally in nature.

Synthetic Elements

Elements $95$ through $118$, which do not occur naturally and were synthesized in laboratories using nuclear accelerators.

Period 1

The periodic table period containing only Hydrogen and Helium, whose electrons occupy only the 1st energy level ($n=1$) within the s block.

Period 6

The periodic row containing $32$ elements ranging from Cesium to Ytterbium, occupying the 6th energy level ($n=6$) and consisting of s, p, d, and f blocks.

Period 7

The periodic row containing $32$ elements ranging from Francium to Nobelium, occupying the 7th energy level ($n=7$) and consisting of s, p, d, and f blocks.

Alkali Metals

Group 1 elements possessing $1$ valence electron.

Alkaline Earth Metals

Group 2 elements possessing $2$ valence electrons.

Pnictogens

The Group 15 (5A) Nitrogen Group elements possessing $5$ valence electrons.

Chalcogens

The Group 16 (6A) Oxygen Group elements possessing $6$ valence electrons.

Halogens

Group 17 (7A) elements possessing $7$ valence electrons.

Noble Gases

Group 18 (8A) elements possessing $8$ valence electrons.

Subshells

Divisions within an electron shell ($s, p, d, f$) that indicate where electrons are arranged within a given energy level ($n$).

Orbitals

Specific regions within a subshell where an electron is probably found, each holding a maximum of $2$ electrons ($s$ has $1$, $p$ has $3$, $d$ has $5$, $f$ has $7$).

Valence Electrons

Electrons found in the outermost shell or energy level of an atom.

Electron Configuration

The notation representing the arrangement of electrons in the sublevels and orbitals of an atom.