Chem part 4: Atoms and Elements

Vocabulary practice flashcards covering atomic structure, subatomic particles, isotopes, electron energy levels, and periodic trends based on Chapter 4 of Timberlake Chemistry (13th Edition).

Atom

The smallest particle of an element that retains the characteristics of that element.

Dalton's Atomic Theory

A scientific theory developed in 1808 by John Dalton proposing that all matter is made up of tiny particles called atoms, all atoms of a given element are identical and distinct from other elements, atoms combine in fixed proportions to form compounds, and chemical reactions involve atom rearrangements without atoms being created or destroyed.

Subatomic Particles

The tiny particles that compose an atom, including protons, neutrons, and electrons, some of which carry electrical charges.

Electron

A negatively charged subatomic particle with an electrical charge of $-1$ and a mass of approximately $0.00055\,\text{amu}$, occupying the large empty space surrounding the nucleus.

Plum-Pudding Model

An early atomic model proposed by J. J. Thomson in 1897 in which electrons and protons were conceived as being randomly distributed in a positively charged spherical cloud like plums embedded in a pudding.

Rutherford's Gold Foil Experiment

A 1911 experiment directed by Ernest Rutherford in which alpha particles were beamed at thin gold foil; the deflection of a small fraction of particles revealed that the atom contains a dense, positively charged nucleus surrounded mostly by empty space.

Nucleus

The small, dense, positively charged region in the center of an atom that contains protons and neutrons and accounts for nearly all the atom's mass.

Proton

A subatomic particle located in the atomic nucleus that possesses a positive electrical charge of $+1$ and a mass of approximately $1.007\,\text{amu}$.

Neutron

An electrically neutral subatomic particle located in the atomic nucleus that possesses a charge of $0$ and a mass of approximately $1.008\,\text{amu}$.

Atomic Mass Unit (amu)

A unit of mass defined by chemists as equal to exactly one-twelfth ($\frac{1}{12}$) of the mass of a carbon atom containing 6 protons and 6 neutrons.

Atomic Number

A whole number specific to each element that equals the total number of protons in an atom, appearing directly above the elemental symbol on the periodic table.

Mass Number

The total number of particles in an atom's nucleus, equal to the sum of the number of protons and neutrons; applies only to individual atoms and does not appear on the periodic table.

Isotopes

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

Atomic Symbol

A standardized notation representing a specific isotope of an element that displays the mass number as an upper-left superscript and the atomic number as a lower-left subscript next to the element's symbol.

Atomic Mass

The weighted average of the masses of all naturally occurring isotopes of an element, calculated relative to carbon-12 and listed below the elemental symbol on the periodic table.

Electromagnetic Radiation

A form of energy consisting of particles that move as waves; forms include radio waves, microwaves, infrared, visible light, ultraviolet, X-rays, and gamma rays.

Wavelength

The distance between consecutive peaks or crests of a wave; inversely related to energy such that shorter wavelengths indicate higher energy.

Electromagnetic Spectrum

The continuous arrangement of electromagnetic radiation across varying wavelengths and frequencies, containing a visible light portion ranging from $700\,\text{nm}$ to $400\,\text{nm}$.

Atomic Spectrum

A series of distinct lines of color separated by dark areas produced when light emitted from a heated element is separated through a prism; unique to each element.

Principal Quantum Number ($n$)

Integer designations ($n = 1, 2, 3\dots$) assigned to specific electron energy levels in an atom, which increase in energy and distance from the nucleus as the value of $n$ increases.

Quantized Energy

The property stating that an electron within an atom can possess only specific, discrete energy values matching fixed energy levels rather than continuous values.

Electron Arrangement

The notation indicating how electrons are distributed among the successive energy levels of an atom (for example, $2,8,1$ for sodium).

Seasonal Affective Disorder (SAD)

A form of depression where individuals experience mood swings and depression during winter, thought to stem from decreased serotonin or increased melatonin due to fewer daylight hours; treatable with a light box.

Valence Electrons

The electrons located in the outermost energy level of an atom; they largely determine the chemical properties of representative elements and correspond to the group number.

Lewis Symbol

A chemical representation where valence electrons are indicated as dots placed around the element's chemical symbol on its sides, top, or bottom.

Periodic Properties

Characteristics of elements (such as atomic size, ionization energy, and metallic character) that predictably increase or decrease across a period and repeat their pattern in each successive period.

Atomic Size

A periodic property determined by the distance of the valence electrons from the nucleus; it increases down a group due to additional energy levels and decreases from left to right across a period due to increased positive nuclear charge.

Ionization Energy

The amount of energy required to remove one of the outermost valence electrons from an atom in the gaseous state; it decreases down a group and increases from left to right across a period.

Metallic Character

The tendency of an element to lose valence electrons easily; it increases going down a group as electrons get farther from the nucleus and decreases across a period from left to right.