Atomic Theory, Structure, and Periodic Table Flashcards

Vocabulary flashcards reviewing historical atomic models, subatomic particles, isotopes, quantum rules for electron configurations, and periodic table classifications based on the lecture material.

Atom

The smallest particle of an element that retains its identity in a chemical reaction.

Dalton's Atomic Theory

A scientific theory stating that all elements are composed of tiny indivisible particles called atoms; atoms of the same element are identical; atoms of different elements combine in simple whole-number ratios to form compounds; and chemical reactions occur when atoms are separated, joined, or rearranged.

Scanning Electron Microscope (SEM)

An instrument that focuses a beam of electrons on a sample to visualize individual atoms and allow scientists to arrange them in patterns.

Electron

A negatively charged subatomic particle ($e^-$) with a relative charge of $1-$, an actual mass of $9.11 \times 10^{-28}\,\text{g}$, and a relative mass of $\frac{1}{1840}$ relative to a proton.

Proton

A positively charged subatomic particle ($p^+$) found in the nucleus with a relative charge of $1+$ and an actual mass of $1.67 \times 10^{-24}\,\text{g}$.

Neutron

A subatomic particle ($n^0$) with no electrical charge (charge of $0$) and a mass approximately equal to that of a proton ($1.67 \times 10^{-24}\,\text{g}$).

Cathode Ray Tube

A sealed glass tube with metal electrodes at each end through which an electric current passes, generating a glowing beam of negatively charged particles deflected by magnetic or electrical fields.

Millikan's Oil Drop Experiment

An experiment that suspended negatively charged oil droplets between electrically charged plates to measure their fall rate, calculating the charge of an electron as $1.60 \times 10^{-19}\,\text{coulombs}$.

Plum Pudding Model

J.J. Thomson's atomic model proposing that electrons were uniformly distributed throughout a sphere filled with positively charged material.

Rutherford's Gold Foil Experiment

An experiment in which positively charged alpha particles were aimed at gold foil, demonstrating that the atom consists mostly of empty space and that its positive charge and mass are concentrated in a dense nucleus.

Nucleus

The tiny, densely packed, positively charged central core of an atom containing protons and neutrons.

Atomic Number

The number of protons in the nucleus of an atom of a specific element.

Mass Number

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

Cation

A positively charged atom or molecule that has fewer electrons than protons.

Anion

A negatively charged atom or molecule that has more electrons than protons.

Isotopes

Atoms of the same element that have the same number of protons but different numbers of neutrons, resulting in different mass numbers.

Atomic Mass

The weighted average mass of the atoms in a naturally occurring sample of an element, reflecting both the mass and percent abundance of each isotope.

Bohr's Atomic Model

An atomic model in which electrons travel in specific circular orbits (energy levels) around the nucleus.

Quantum

The exact amount of energy required for an electron to move from one energy level to another energy level.

Quantum Mechanical Model

The modern mathematical model of the atom developed by Schrödinger that restricts electron energy levels but does not specify an exact orbital path for electrons.

Electron Cloud

A region around the nucleus where there is a high probability of finding an electron, represented by probability density.

Atomic Orbital

A pictorial or mathematical region of space where there is a high probability of finding an electron.

Valence Electrons

Electrons located in the outermost principal energy level of an atom, determined by the element's group number on the periodic table.

Aufbau Principle

The rule stating that electrons occupy the orbitals of lowest energy first before occupying higher energy levels.

Pauli Exclusion Principle

The rule stating that an atomic orbital can hold at most two electrons, and those two electrons must have opposite spins ($\uparrow \downarrow$).

Hund's Rule

The rule stating that electrons occupy orbitals of equal energy in a way that maximizes the number of electrons with the same spin direction before pairing up.

Triad

A group of three elements with similar chemical properties in Döbereiner's classification system, where the middle element's atomic mass is approximately the average of the other two.

Mendeleev's Periodic Table

An arrangement of elements ordered by increasing atomic mass into rows of repeating similar properties, which allowed for predicting undiscovered elements.

Modern Periodic Table

An arrangement of elements organized by increasing atomic number into periods (rows) and groups (columns).

Metal

An element that is a good conductor of heat and electricity, possesses luster, is malleable and ductile, and is solid at room temperature (except mercury).

Nonmetal

An element that generally lacks metallic properties, is a poor conductor of heat and electricity, and is brittle in solid form.

Metalloid

An element that exhibits properties similar to both metals and nonmetals depending on environmental conditions.

Alkali Metals

The elements occupying Group 1A of the periodic table.

Alkaline Earth Metals

The elements occupying Group 2A of the periodic table.

Halogens

The nonmetallic elements occupying Group 7A of the periodic table.

Noble Gases

The inactive elements in Group 8A of the periodic table characterized by completely filled $s$ and $p$ sublevels in their outermost energy level.

Representative Elements

Elements in Groups 1A through 7A of the periodic table that display a broad spectrum of physical and chemical properties and have partially filled $s$ or $p$ sublevels.

Transition Metals

Group B elements located in the main body of the periodic table whose highest occupied $s$ sublevel and nearby $d$ sublevel contain electrons.

Inner Transition Metals

Elements located below the main body of the periodic table whose highest occupied $s$ sublevel and nearby $f$ sublevel contain electrons.