Vocabulary List: Atomic Theorists and Structures of the Atom
Overview
Grade Level: 9th Grade
Topic: Atomic theorists and the structures of the atom.
Number of Words: 50
Vocabulary Words
Atom
Definition: The basic unit of matter, consisting of a nucleus surrounded by electrons.
Example: Every chemical element is made up of atoms.
Proton
Definition: A positively charged subatomic particle located in the nucleus of an atom.
Example: The number of protons in an atom determines its atomic number.
Neutron
Definition: A neutral subatomic particle found in the nucleus of an atom, contributing to its mass.
Example: Neutrons play a key role in the stability of atomic nuclei.
Electron
Definition: A negatively charged subatomic particle that orbits the nucleus of an atom.
Example: Electrons are involved in chemical bonding and reactions.
Nucleus
Definition: The dense central core of an atom that contains protons and neutrons.
Example: The nucleus is much smaller than the overall size of the atom.
Atomic number
Definition: The number of protons in the nucleus of an atom, which determines the element.
Example: Carbon has an atomic number of six because it has six protons.
Mass number
Definition: The total number of protons and neutrons in the nucleus of an atom.
Example: The mass number of an element is used to identify isotopes.
Isotope
Definition: Atoms of the same element that have the same number of protons but different numbers of neutrons.
Example: Carbon-14 is a well-known isotope used in radiocarbon dating.
Ion
Definition: An atom or molecule that has gained or lost one or more electrons, resulting in a net charge.
Example: When sodium loses an electron, it becomes a positively charged ion.
Atomic mass
Definition: The weighted average mass of an element’s isotopes, measured in atomic mass units (AMU).
Example: The atomic mass of chlorine is approximately 35.5 AMU.
Chemical bond
Definition: The lasting attraction between atoms, ions, or molecules that enables the formation of chemical compounds.
Example: Ionic bonds and covalent bonds are two common types of chemical bonds.
Quantum theory
Definition: A theory in physics that describes the behavior of matter and energy at atomic and subatomic levels.
Example: Quantum theory explains the behavior of electrons around the nucleus.
Heisenberg Uncertainty Principle
Definition: The principle stating that it is impossible to simultaneously know the exact position and momentum of a particle.
Example: The Heisenberg Uncertainty Principle challenges classical mechanics with its implications.
Bohr model
Definition: A model of the atom that depicts electrons traveling in fixed orbits around the nucleus.
Example: In the Bohr model, electrons occupy quantized energy levels.
Orbital
Definition: A region in an atom where there is a high probability of finding electrons.
Example: Each orbital can hold a maximum of two electrons.
Electron cloud
Definition: The regions around the nucleus where electrons are likely to be found.
Example: The electron cloud represents the probabilistic location of an atom's electrons.
Energy level
Definition: The specific energies that electrons can have when in an atom.
Example: Electrons can only exist in certain energy levels around the nucleus.
Valence electron
Definition: An electron in the outermost shell of an atom that can participate in chemical bonding.
Example: The number of valence electrons determines how an element reacts.
Subatomic particle
Definition: Particles smaller than atoms, including protons, neutrons, and electrons.
Example: The three main types of subatomic particles are protons, neutrons, and electrons.
Dalton's theory
Definition: A theory proposed by John Dalton postulating that all matter is made of atoms, which are indivisible and identical for each element.
Example: Dalton's theory laid the groundwork for modern atomic science.
Thomson's model
Definition: The atomic model proposed by J.J. Thomson, suggesting atoms contain smaller particles (electrons) within a positively charged sphere.
Example: The 'plum pudding' model was J.J. Thomson's visualization of atomic structure.
Rutherford's experiment
Definition: An experiment that proved atoms have a small, dense nucleus surrounded by mostly empty space.
Example: Rutherford's gold foil experiment transformed the understanding of atomic structure.
Planck's theory
Definition: A theory developed by Max Planck stating that energy is quantized and comes in discrete units called quanta.
Example: Planck's theory revolutionized the field of quantum mechanics.
Mole
Definition: A unit representing particles, used to measure amount of substance.
Example: One mole of carbon contains approximately atoms.
Electromagnetic force
Definition: A fundamental force of nature responsible for interactions between charged particles.
Example: Electromagnetic forces hold electrons in orbit around the atomic nucleus.
Friedrich Hund
Definition: A scientist known for Hund's rule which states that electrons occupy degenerate orbitals singly before pairing up.
Example: Hund's rule explains the electron configuration of elements.
Erwin Schrodinger
Definition: A physicist known for developing the wave equation that describes how electrons behave as waves.
Example: Schrodinger's wave equation is a key component of quantum mechanics.
James Chadwick
Definition: The physicist who discovered the neutron, leading to a deeper understanding of atomic structure.
Example: Chadwick's discovery of the neutron was pivotal in the development of atomic theory.
Electron configuration
Definition: The arrangement of electrons in an atom’s orbitals.
Example: Understanding electron configuration is crucial for predicting an element's chemical properties.
Pauli Exclusion Principle
Definition: A principle stating that no two electrons can occupy the same quantum state simultaneously within an atom.
Example: The Pauli Exclusion Principle helps explain the arrangement of electrons in atoms.
Lewis dot structure
Definition: A diagram that represents the valence electrons of an atom as dots around the atomic symbol.
Example: Lewis dot structures are helpful in visualizing bonding in molecules.
Chemical reaction
Definition: A process that involves the rearrangement of the molecular or ionic structure of a substance.
Example: Chemical reactions often result in the formation of new substances.
Electrostatic force
Definition: The force between charged particles that can attract or repel them based on their charges.
Example: Electrostatic forces are crucial in understanding atomic interactions.
Quantum mechanical model
Definition: The modern model of the atom that incorporates the principles of quantum mechanics.
Example: The quantum mechanical model provides a more accurate depiction of electron behavior.