Atoms and the Periodic Table

Vocabulary practice flashcards covering atomic theory, subatomic particles, atomic models, electron configuration, periodic table structure, and periodic trends.

Atom

The basic building block of all matter.

Plum Pudding Model

The atomic model proposed by J.J. Thomson (also referred to as the blueberry muffin model), which describes the atom as a sphere of positive charge embedded with negatively charged electrons to maintain overall neutrality.

Rutherford's Gold Foil Experiment

An experiment where a beam of alpha particles was directed from a lead shield block through slits onto a sheet of gold foil surrounded by a scintillation screen, proving that atoms consist mostly of empty space with a dense, positively charged center.

Planetary Model

Ernest Rutherford's atomic model positing that atoms are mostly empty space containing a small, dense, positively charged nucleus made of protons, with electrons circling around it.

Bohr's Atomic Model

An atomic model established by Niels Bohr proposing that electrons travel in fixed, specific energy levels, shells, or orbits to avoid being pulled into the nucleus.

James Chadwick's Atomic Contribution

The proposal and discovery of neutrons—neutral particles within the nucleus that prevent proton repulsion and hold the nucleus together.

Simplified Atomic Model (SAM)

A composite atomic model synthesizing findings from Thomson, Rutherford, Bohr, and Chadwick, defining the atom as mostly empty space composed of a central nucleus and surrounding electron shells/orbits.

Proton ($p^+$)

A positively charged subatomic particle situated in the nucleus of an atom that carries an atomic mass of $1\,\text{a.m.u.}$

Neutron ($n$)

A neutral subatomic particle with no electrical charge located in the nucleus, having an atomic mass of $1\,\text{a.m.u.}$

Electron ($e^-$)

A tiny, negatively charged subatomic particle situated outside the nucleus in electron shells, considered to have negligible or no mass.

Atomic Number

The whole number located in the top-left corner of an element box that equals the total number of protons and serves as a unique identifier for each element.

Atomic Mass (Mass Number)

The total mass of an atom measured in atomic mass units ($\text{a.m.u.}$), equal to the sum of the protons and neutrons ($\text{Atomic Mass} = \text{protons} + \text{neutrons}$).

Rules for Electron Configuration

Principles dictating that electrons must fill the shell closest to the nucleus first and completely fill each orbital before moving outwards, with maximum limits of $2\,e^-$ in shell 1, $8\,e^-$ in shell 2, and $8\,e^-$ in shell 3.

Valence Electrons

The specific electrons located in the outermost (last) shell of an atom.

Electron Configuration Shorthand

A simplified notation listing the number of electrons in each shell from innermost to outermost separated by commas (such as $2e^-, 3e^-$ for Boron).

Mendeleev's Periodic Table

The original periodic table created by Dmitri Mendeleev, which arranged elements by increasing atomic mass, grouped chemicals with identical behaviors into vertical columns, and predicted yet-undiscovered elements.

Modern Periodic Table

The organizational arrangement of all known and unknown elements ordered by increasing atomic number, structured into columns of families/groups and rows of periods.

Group (Family)

A vertical column on the periodic table whose member elements possess the same number of valence electrons (matching the Roman numeral of A groups) and display identical chemical reactivity.

Transition Metals

The metallic elements belonging to the B groups that occupy the central section of the periodic table.

Period

A horizontal row on the periodic table that indicates the total number of occupied electron shells an element possesses.

Metals

A classification of elements characterized by metallic sheen, malleability, ductility, and high electrical and thermal conductivity, all of which are solid at STP except mercury.

Non-metals

Elements that do not conduct heat or electricity.

Metalloids

Elements positioned along the boundary between metals and non-metals that exhibit intermediate conductivity and function as semiconductors.

Alkali Metals (Group IA)

A group of very soft, extremely reactive metals (especially with water) containing $1$ valence electron, occupying column 1 of the periodic table excluding hydrogen.

Alkaline Earth Metals (Group IIA)

A family of elements in Group IIA containing $2$ valence electrons, commonly found in rocks and exhibiting reactivity less vigorous than alkali metals.

Halogens (Group VIIA)

The family of elements situated in Group VIIA that have $7$ valence electrons and are recognized as the most reactive non-metallic elements.

Inert Gases (Noble Gases / Group VIIIA)

A group of chemically non-reactive, highly stable elements containing $8$ valence electrons in their outermost shell, with the exception of helium which has $2$.

Standard Temperature and Pressure (STP)

Reference physical conditions defined as a temperature of $0\,^\circ\text{C}$ and a pressure of $101.3\,\text{kPa}$, under which most elements are solids, $2$ are liquids ($\text{Hg}$ and $\text{Br}$), and $11$ are gases.

Isotopes

Atoms belonging to the same element that have an identical number of protons but differ in their number of neutrons, leading to distinct atomic mass numbers while maintaining identical chemical properties.

Relative Atomic Mass

The decimal value listed on the periodic table calculated as the weighted average mass of an element's naturally occurring isotopes based on their relative percentage abundances.

Atomic Radius

The measurement of the distance from the atomic nucleus to the outermost electron shell, which increases moving down a group and decreases moving from left to right across a period.

Electronegativity

A property describing an atom's ability to attract and hold onto electrons, which increases as atomic radius decreases across a period and up a group.