Atomic Structure, Historical Models, and the Periodic Table

Comprehensive vocabulary flashcards covering atomic structure, subatomic particles, historical atomic models (Democritus, Dalton, Thomson, Rutherford, Bohr, Chadwick), electron energy levels, isotopes, and Bohr diagram rules.

Democritus

Ancient Greek philosopher who believed all matter was made up of extremely small particles that could not be divided, calling them atoms (meaning uncut).

John Dalton

Chemist who proposed an atomic theory based on experimental evidence, inferring that atoms had specific characteristics.

Dalton's Atomic Theory

Theory stating that all matter is made of indivisible, indestructible atoms, all atoms of the same element are identical in mass and properties, compounds form by combining different atoms, and chemical reactions are rearrangements of atoms.

Dalton's Model Error

The incorrect assumption that atoms were like smooth, hard balls that could not be broken into smaller pieces.

Joseph Thomson

Physicist who hypothesized and confirmed that atoms contained negatively charged subatomic particles called electrons.

Plum Pudding Model

Atomic model proposed by Joseph Thomson describing a neutral atom filled with a positively charged mass of matter containing scattered negatively charged electrons (analogous to chocolate chips in ice cream).

Ernest Rutherford

Physicist who conducted the gold foil experiment and concluded that an atom's positive charge is concentrated in a dense central region called the nucleus.

Gold Foil Experiment

Experiment where positively charged particles were shot at thin gold foil; most passed through straight, but some deflected or bounced straight back upon approaching the positively charged nucleus.

Nucleus

The dense, positively charged mass located in the center of an atom that contains protons and neutrons.

Niels Bohr

Scientist who proposed that electrons move in fixed orbits around the nucleus at constant speeds and possess specific amounts of energy.

Planetary Model

Bohr's model of the atom comparing electrons moving in orbit around the nucleus to planets revolving around the sun.

Energy Levels

The fixed orbits surrounding a nucleus where electrons travel, moving from one level to another when the atom gains or loses specific amounts of energy.

Electron Cloud Model

Modern atomic model revised in the 1920s that represents the most likely locations and movement of electrons within orbitals.

Atomic Orbital

A region of space around the nucleus where an electron is likely to be located based on its energy level.

Electron Configuration

The arrangement of electrons in the orbitals of an atom, which is most stable when electrons occupy orbitals with the lowest possible energies.

Propeller Analogy

A visual model for electron location; like a spinning airplane propeller whose blades form a blur, electrons are somewhere within the cloud but their exact position at any moment cannot be pinpointed.

James Chadwick

Scientist who discovered the neutron, a hard-to-detect subatomic particle in the nucleus with no charge and mass nearly equal to a proton.

Proton

A positively charged ($+\text{charge}$) subatomic particle located in the nucleus of an atom.

Electron

A negatively charged ($-\text{charge}$) subatomic particle found outside the nucleus with a mass approximately $1/2000$ of a proton.

Neutron

A subatomic particle in the nucleus with no charge and a mass almost identical to that of a proton.

Atomic Number

The unique number of protons in the nucleus of an atom of an element, which also equals the number of electrons in a neutral atom.

Mass Number

The total sum of protons and neutrons located in the nucleus of an atom.

Neutron Calculation Formula

Equation used to determine neutron quantity: $\text{Number of Neutrons} = \text{Mass Number} - \text{Atomic Number}$.

Isotopes

Atoms of the same element that have the same number of protons and electrons, but different numbers of neutrons.

Isotope Naming Notation

Standard method used to distinguish isotopes by writing the element name followed by a hyphen and its mass number (e.g., Carbon-12).

Weighted Average Atomic Mass

The atomic mass value listed on the periodic table, which depends on the natural distribution of an element's isotopes and their individual masses.

Periodic Table Tile Information

The four standard pieces of information provided for each element: name, symbol, atomic number, and atomic mass.

First Energy Level Capacity

The innermost electron orbit, which can hold a maximum of $2$ electrons.

Second Energy Level Capacity

The second electron orbit, which can hold a maximum of $8$ electrons.

Third Energy Level Capacity

The third electron orbit, which holds up to $8$ electrons for early periodic elements (and up to $18$ electrons max in full orbital configurations).

Fourth Energy Level Capacity

The fourth electron orbit, which can hold a maximum of $18$ electrons.

Period Number Significance

The horizontal row number on the periodic table indicating the total number of energy levels (shells) an atom possesses.

Counter-Clockwise Drawing Rule

Rule for drawing Bohr diagrams where electrons beyond the first shell are added one at a time starting on the right side and proceeding counter-clockwise.

Neutral Atom

An atom with no overall electrical charge ($+/-$) because its total number of positive protons equals its total number of negative electrons.

Carbon Bohr Diagram Structure

Bohr model representation of Carbon (atomic number $6$) containing $2$ shells with $2$ electrons in the 1st shell and $4$ electrons in the 2nd shell.

Carbon-12 vs Carbon-14

Comparison of Carbon isotopes: Carbon-12 has $6$ protons, $6$ neutrons, and $6$ electrons, while Carbon-14 has $6$ protons, $8$ neutrons, and $6$ electrons.

Uranium Atomic Number Practice

Practice example demonstrating that Uranium-238 (with $146$ neutrons) and Uranium-235 (with $143$ neutrons) both share an atomic number of $92$.

Aluminum Bohr Atom Specifications

Bohr representation of Aluminum ($\text{Atomic Number} = 13$, $\text{AMU} = 27$) having $13$ protons, $14$ neutrons, and $13$ electrons ($2$ in 1st level, $8$ in 2nd level, $3$ in 3rd level).

Helium Bohr Atom Specifications

Bohr representation of Helium ($\text{Atomic Number} = 2$) located in period $1$, containing $2$ protons and $2$ electrons filling its single energy shell.

Lithium Symbol Notation ($^{7}_{3}\text{Li}$)

Standard chemical symbol notation for Lithium showing a mass number of $7$ and atomic number of $3$, representing $3$ protons, $4$ neutrons, and $3$ electrons.