The Structure of the Atom
Big Idea
The first theories of the "atom" were developed by two 5th-century BC Greek philosophers: Leucippus of Miletus (an ancient Greek city in what is now Turkey) and Democritus of Abdera (in the region of modern Thrace, Greece). Their concepts of atomism were not especially experimental in origin, however they were correct in their reasoning that if you could examine matter on ever smaller scales (which was beyond their ability - well before the invention of the microscope) then eventually you could see individual atoms - the smallest particle of matter that could not be divided further. Leucippus and Democritus reasoned that the different physical properties of matter - such as color, hardness, etc. - could be explained by the different shapes and/or arrangements of atoms in the material.
The first theories of the "atom" were developed by two 5th-century BC Greek philosophers: Leucippus of Miletus (an ancient Greek city in what is now Turkey) and Democritus of Abdera (in the region of modern Thrace, Greece). Their concepts of atomism were not especially experimental in origin, however they were correct in their reasoning that if you could examine matter on ever smaller scales (which was beyond their ability - well before the invention of the microscope) then eventually you could see individual atoms - the smallest particle of matter that could not be divided further. Leucippus and Democritus reasoned that the different physical properties of matter - such as color, hardness, etc. - could be explained by the different shapes and/or arrangements of atoms in the material.
Supplemental Readings
An Introduction to Chemistry (introductory textbook by Mark Bishop):
Ch.3 - The Structure of Matter and the Chemical Elements
Section 3.2 pp. 80 - 83 and Section 3.4 pp. 88 - 94
GenChem Level Videos
Atoms, Molecules, and Ions: Part 1 of 8 by Mike Christiansen [8:45]
In this video, Dr. Christiansen explains the periodic table, including definitions of the following terms: group, period, alkali metal, alkaline earth metal, halogen, noble gas, metal, nonmetal, and metalloid. He'll also teach you the definition of the terms neutrons, protons, and electrons.
Atoms, Molecules, and Ions: Part 2 of 8 by Mike Christiansen [11:20]
In this video,Dr. Christiansen will teach you how to write chemical symbols for elements (including isotopes) and how to calculate elements’ atomic weights from their relative isotopic abundances.
Dalton's Atomic Theory by Ben's Chem Videos [5:31]
Law of Definite Proportions by Ben's Chem Videos [3:53]
Law of Multiple Proportions by Ben's Chem Videos [4:38]
Practice with Isotope Notation by Ben's Chem Videos [6:06]
Atoms and Elements Playlist by by Ben's Chem Videos
Introductory Level Videos
Basic Atomic Structure: A Look Inside the Atom by Tyler DeWitt [7:44] What does the inside of an atom look like? Here, we'll look at the subatomic particles ( protons, neutrons, and electrons) that make up the atom. We'll see how the electrons orbit the nucleus, and talk about the masses of protons, neutrons, and electrons in amu, or atomic mass unit.
What's the Difference between an Atom and a Molecule? by Tyler DeWitt [5:16]
Never be confused by this concept again! In this video, we talk about the difference between an atom and molecule, and discuss the nucleus, energy levels, protons and neutrons, compounds, covalent bonding, sharing electrons, and lego blocks.
Atomic Number, Mass Number, and Net Charge by Tyler DeWitt [6:26]
How do you calculate and determine atomic number, mass number, and net charge? Atomic number is the number of protons in an atom. Mass number is the number of neutrons in an atom, and net charge describes how the protons and electrons balance out.
What's an Ion? by Tyler DeWitt [6:52]
Confused about ions? We'll learn the difference between an atom and an ion. Ions are formed because of a net charge on an atom, because the number of protons and electrons do not balance. This means that the atom is no longer electrically neutral, but is a cation or an anion. We also talk about polyatomic ions.
Practice Problems: Net Charge, Mass Number, Atomic Number by Tyler DeWitt [4:56]
Practice and example problems to help you learn how to determine and calculate the net charge, mass number, and atomic number of atoms. Also we'll look at how to determine the number of protons, neutrons, and electrons in an atom.
What are Isotopes? by Tyler DeWitt [7:56]
We'll learn about what isotopes are and how to write atomic number and mass number in isotope notation. We talk about a simple analogy with cars to explain this tutorial. Isotopes are versions of an atom or an element that have the same number of protons, but different numbers of neutrons. Isotopes and isotope notation are particularly important in nuclear chemistry.
Isotope Notation by Tyler DeWitt [7:56]
Learn how to write atoms in isotope notation! In isotope notation, you can quickly show how many protons, neutrons, and electrons are in an atom. You put the atomic number, mass number, and net charge around the chemical element symbol. Isotope notation is particularly important in nuclear chemistry, because if you're doing fission, fusion, alpha decay, beta decay, positron emission, or electron capture, you want to be able to tell how many neutrons and protons are in the nucleus.
Isotopes and Elements Practice Problems by Tyler DeWitt [12:49]
In this video we'll look at how to determine, calculate and solve for atomic number, mass number, isotopes, net charge, protons, neutrons, and electrons. We'll determine what element an atom is by using the periodic table.
Additional Resources
Advanced Readings
The Idea of the Atom Chem1 General Chemistry Virtual Textbook by Stephen Lower
Answers the question "Atoms and elements: what's the difference?"
Atoms Become Real Chem1 General Chemistry Virtual Textbook
How evidence of the atom was interpreted and how we can now "see" individual atoms!
Laws of chemical change Chem1 General Chemistry Virtual Textbook
Overview of the Law of Definite Proportions and the Law of Multiple Proportions
The Nuclear Atom Chem1 General Chemistry Virtual Textbook
A small, dense nucleus and an much larger "electron cloud" make up the modern concept of the nuclear atom. Atomic number, mass number, isotopes, and atomic weights are explained. Be sure to read and review the concepts through the bottom of the page.
The Nuclear Atom Concept Map from Chem1 General Chemistry Virtual Textbook may be of help in organizing your knowledge of the topics.
Animations/Simulations
Atomic Symbols, Atomic Numbers, and Mass Numbers by Wisc-Online
Ions by Wisc-Online
Isotopes by Wisc-Online
Build an Atom by PhET - University of Colorado
Rutherford Scattering by PhET - University of Colorado
Additional Video
History of the Atom by BozemanScience [9:09]
An Introduction to Chemistry (introductory textbook by Mark Bishop):
Ch.3 - The Structure of Matter and the Chemical Elements
Section 3.2 pp. 80 - 83 and Section 3.4 pp. 88 - 94
GenChem Level Videos
Atoms, Molecules, and Ions: Part 1 of 8 by Mike Christiansen [8:45]
In this video, Dr. Christiansen explains the periodic table, including definitions of the following terms: group, period, alkali metal, alkaline earth metal, halogen, noble gas, metal, nonmetal, and metalloid. He'll also teach you the definition of the terms neutrons, protons, and electrons.
Atoms, Molecules, and Ions: Part 2 of 8 by Mike Christiansen [11:20]
In this video,Dr. Christiansen will teach you how to write chemical symbols for elements (including isotopes) and how to calculate elements’ atomic weights from their relative isotopic abundances.
Dalton's Atomic Theory by Ben's Chem Videos [5:31]
Law of Definite Proportions by Ben's Chem Videos [3:53]
Law of Multiple Proportions by Ben's Chem Videos [4:38]
Practice with Isotope Notation by Ben's Chem Videos [6:06]
Atoms and Elements Playlist by by Ben's Chem Videos
Introductory Level Videos
Basic Atomic Structure: A Look Inside the Atom by Tyler DeWitt [7:44] What does the inside of an atom look like? Here, we'll look at the subatomic particles ( protons, neutrons, and electrons) that make up the atom. We'll see how the electrons orbit the nucleus, and talk about the masses of protons, neutrons, and electrons in amu, or atomic mass unit.
What's the Difference between an Atom and a Molecule? by Tyler DeWitt [5:16]
Never be confused by this concept again! In this video, we talk about the difference between an atom and molecule, and discuss the nucleus, energy levels, protons and neutrons, compounds, covalent bonding, sharing electrons, and lego blocks.
Atomic Number, Mass Number, and Net Charge by Tyler DeWitt [6:26]
How do you calculate and determine atomic number, mass number, and net charge? Atomic number is the number of protons in an atom. Mass number is the number of neutrons in an atom, and net charge describes how the protons and electrons balance out.
What's an Ion? by Tyler DeWitt [6:52]
Confused about ions? We'll learn the difference between an atom and an ion. Ions are formed because of a net charge on an atom, because the number of protons and electrons do not balance. This means that the atom is no longer electrically neutral, but is a cation or an anion. We also talk about polyatomic ions.
Practice Problems: Net Charge, Mass Number, Atomic Number by Tyler DeWitt [4:56]
Practice and example problems to help you learn how to determine and calculate the net charge, mass number, and atomic number of atoms. Also we'll look at how to determine the number of protons, neutrons, and electrons in an atom.
What are Isotopes? by Tyler DeWitt [7:56]
We'll learn about what isotopes are and how to write atomic number and mass number in isotope notation. We talk about a simple analogy with cars to explain this tutorial. Isotopes are versions of an atom or an element that have the same number of protons, but different numbers of neutrons. Isotopes and isotope notation are particularly important in nuclear chemistry.
Isotope Notation by Tyler DeWitt [7:56]
Learn how to write atoms in isotope notation! In isotope notation, you can quickly show how many protons, neutrons, and electrons are in an atom. You put the atomic number, mass number, and net charge around the chemical element symbol. Isotope notation is particularly important in nuclear chemistry, because if you're doing fission, fusion, alpha decay, beta decay, positron emission, or electron capture, you want to be able to tell how many neutrons and protons are in the nucleus.
Isotopes and Elements Practice Problems by Tyler DeWitt [12:49]
In this video we'll look at how to determine, calculate and solve for atomic number, mass number, isotopes, net charge, protons, neutrons, and electrons. We'll determine what element an atom is by using the periodic table.
Additional Resources
Advanced Readings
The Idea of the Atom Chem1 General Chemistry Virtual Textbook by Stephen Lower
Answers the question "Atoms and elements: what's the difference?"
Atoms Become Real Chem1 General Chemistry Virtual Textbook
How evidence of the atom was interpreted and how we can now "see" individual atoms!
Laws of chemical change Chem1 General Chemistry Virtual Textbook
Overview of the Law of Definite Proportions and the Law of Multiple Proportions
The Nuclear Atom Chem1 General Chemistry Virtual Textbook
A small, dense nucleus and an much larger "electron cloud" make up the modern concept of the nuclear atom. Atomic number, mass number, isotopes, and atomic weights are explained. Be sure to read and review the concepts through the bottom of the page.
The Nuclear Atom Concept Map from Chem1 General Chemistry Virtual Textbook may be of help in organizing your knowledge of the topics.
Animations/Simulations
Atomic Symbols, Atomic Numbers, and Mass Numbers by Wisc-Online
Ions by Wisc-Online
Isotopes by Wisc-Online
Build an Atom by PhET - University of Colorado
Rutherford Scattering by PhET - University of Colorado
Additional Video
History of the Atom by BozemanScience [9:09]