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This is the second part of a classroom-tested learning module on the development of atomic theory. It focuses on the discovery of ions, isotopes, and electron shells. The key idea is that, while the number of protons in an atom remains constant, the number of electrons and neutrons can vary. It includes simple simulations of a hydrogen ion, a hydrogen isotope, energy levels in an "electron shell" model of the atom, and animations of electron configurations for the first eleven elements. See Related Materials for a link to Part One of this series.
Please note that this resource requires
Editor's Note:This tutorial could be highly useful to elementary teachers seeking additional content knowledge in the basics of atomic structure. The conversational language is appropriate for high school students as well. Don't miss the "Questions and Quizzes" and links to additional resources on the topic.
Bohr model, Neils Bohr, atomic structure, charged particles, electron, electron excitation, history of atom, history of the atom, hydrogen atom, ion, isotope, neutron, nuclear structure, nucleus, proton, stable element, structure of the nucleus, unstable element
Metadata instance created
July 12, 2011
by Caroline Hall
October 10, 2012
by Caroline Hall
Last Update when Cataloged:
April 30, 2006
AAAS Benchmark Alignments (2008 Version)
4. The Physical Setting
4D. The Structure of Matter
6-8: 4D/M1a. All matter is made up of atoms, which are far too small to see directly through a microscope.
9-12: 4D/H1. Atoms are made of a positively charged nucleus surrounded by negatively charged electrons. The nucleus is a tiny fraction of the volume of an atom but makes up almost all of its mass. The nucleus is composed of protons and neutrons which have roughly the same mass but differ in that protons are positively charged while neutrons have no electric charge.
9-12: 4D/H2. The number of protons in the nucleus determines what an atom's electron configuration can be and so defines the element. An atom's electron configuration, particularly the outermost electrons, determines how the atom can interact with other atoms. Atoms form bonds to other atoms by transferring or sharing electrons.
9-12: 4D/H3. Although neutrons have little effect on how an atom interacts with other atoms, the number of neutrons does affect the mass and stability of the nucleus. Isotopes of the same element have the same number of protons (and therefore of electrons) but differ in the number of neutrons.
4E. Energy Transformations
9-12: 4E/H5. When energy of an isolated atom or molecule changes, it does so in a definite jump from one value to another, with no possible values in between. The change in energy occurs when light is absorbed or emitted, so the light also has distinct energy values. The light emitted or absorbed by separate atoms or molecules (as in a gas) can be used to identify what the substance is.
4G. Forces of Nature
9-12: 4G/H3. Most materials have equal numbers of protons and electrons and are therefore electrically neutral. In most cases, a material acquires a negative charge by gaining electrons and acquires a positive charge by losing electrons. Even a tiny imbalance in the number of protons and electrons in an object can produce noticeable electric forces on other objects.
9-12: 4G/H6. The nuclear forces that hold the protons and neutrons in the nucleus of an atom together are much stronger than the electric forces between the protons and electrons of the atom. That is why much greater amounts of energy are released from nuclear reactions than from chemical reactions.
10. Historical Perspectives
10F. Understanding Fire
9-12: 10F/H3. In the early 1800s, British chemist and physicist John Dalton united the concepts of atoms and elements. He proposed two ideas that laid the groundwork for modern chemistry: first, that elements are formed from small, indivisible particles called atoms, which are identical for a given element but different from any other element; and second, that chemical compounds are formed from atoms by combining a definite number of each type of atom to form one molecule of the compound.
9-12: 10F/H4. Dalton figured out how the relative weights of the atoms could be determined experimentally. His idea that every substance had a unique atomic composition provided an explanation for why substances were made up of elements in specific proportions.
11. Common Themes
6-8: 11B/M1. Models are often used to think about processes that happen too slowly, too quickly, or on too small a scale to observe directly. They are also used for processes that are too vast, too complex, or too dangerous to study.
6-8: 11B/M4. Simulations are often useful in modeling events and processes.
6-8: 11D/M3. Natural phenomena often involve sizes, durations, and speeds that are extremely small or extremely large. These phenomena may be difficult to appreciate because they involve magnitudes far outside human experience.
Common Core State Reading Standards for Literacy in Science and Technical Subjects 6—12
Range of Reading and Level of Text Complexity (6-12)
RST.11-12.10 By the end of grade 12, read and comprehend science/technical texts in the grades 11—CCR text complexity band independently and proficiently.
This resource is part of a Physics Front Topical Unit.
Topic: Particles and Interactions and the Standard Model Unit Title: History and Discovery
This is the second part of a classroom-tested learning module on the development of atomic theory. It focuses on the discovery of ions, isotopes, and electron shells. The key idea is that, while the number of protons in an atom remains constant, the number of electrons and neutrons can vary. It includes simple simulations of a hydrogen ion, a hydrogen isotope, energy levels in an "electron shell" model of the atom, and more.
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