models of the atom assignment

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Course info.

• Prof. Donald Sadoway

Departments

• Materials Science and Engineering

As Taught In

• Chemical Engineering

Learning Resource Types

Introduction to solid state chemistry, 3. atomic models: rutherford & bohr.

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Session Overview

Prerequisites.

Before starting this session, you should be familiar with:

• Session 2: The Periodic Table

Looking Ahead

Prof. Sadoway discusses the atomic spectra of hydrogen ( Session 4 ).

Learning Objectives

After completing this session, you should be able to:

• Understand Thomson’s “plum pudding” model .
• Understand Rutherford’s “nuclear” model .
• Explain the Bohr model of hydrogen .
• Understand Bohr’s quantization condition.

Archived Lecture Notes #1 (PDF) , Sections 1-3

Lecture Video

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Lecture Slides (PDF - 9.3MB)

Periodic Table and Table of Constants

Lecture Summary

Prof. Sadoway talks about the principles of modern chemistry and how that led to the understanding of the structure of the atom . He details Bohr’s postulates for the hydrogen atom and discusses how the Planck-Einstein relationship applies to electron transitions. He defines the different isotopes of hydrogen.

This lecture includes the following:

• Electrons are distributed uniformly throughout the atom
• Conclusions from the gold foil experiment
• Majority of the mass is found in the nucleus
• Electrons orbit around the nucleus
• Explanation of blackbody radiation and atomic spectra
• Electrons follow circular orbits around a nucleus
• Orbital angular momentum is quantized hence only certain orbits are possible
• Electrons in stable orbits do not radiate
• Electrons change orbits by radiating or absorbing photons

Problems (PDF)

Solutions (PDF)

Textbook Problems

For further study, supplemental readings.

Ottaviani, J. Suspended in Language: Niels Bohr’s Life, Discoveries, and the Century He Shaped . GT Labs: Ann Arbor, MI, 2004. ISBN: 9780978803728.

Rozental, S. Niels Bohr: His Life and Work as Seen by His Friends and Colleagues . New York, NY: Wiley, 1967.

Bohr, Niels H. D. On the Constitution of Atoms and Molecules . New York, NY: W.A. Benjamin, 1963.

Bohr, Niels H. D. Atomic Physics and Human Knowledge . New York, NY: Wiley, 1958.

Bohr, Niels. “ On the Constitution of Atoms and Molecules. ” Philosophical Magazine Series 6 26 (July 1913): 1-15.

Cathcart, B. The Fly in the Cathedral: How a Small Group of Cambridge Scientists Won the Race to Split the Atom . New York, NY: Penguin, 2005. ISBN: 9780670883219.

Andrade, E. N. Rutherford and the Nature of the Atom . Garden City, NY: Doubleday, 1964.

Frayn, M. Copenhagen: A Play in Two Acts . New York, NY: S. French, 2000.

Miller, D. P. Discovering Water: James Watt, Henry Cavendish and the Nineteenth Century Water Controversy . Burlington, VT: Ashgate, 2004. ISBN: 9780754631774.

Cavendish Laboratory

How Atoms Work

Joseph Thompson - 1906 Nobel Prize in Physics

Ernest Rutherford - 1908 Nobel Prize in Chemistry

Johannes Geiger

Ernest Marsden

Max Planck - 1918 Nobel Prize in Physics

Albert Einstein - 1921 Nobel Prize in Physics

Niels Bohr - 1922 Nobel Prize in Physics

Robert Millikan - 1923 Nobel Prize in Physics

Henry Cavendish

Werner Heisenberg - 1932 Nobel Prize in Physics

Harold Urey - 1934 Nobel Prize in Chemistry

Charles-Augustin de Coulomb

James Prescott Joule

Other OCW and OER Content

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Timeline of atomic models

1. Model of Democritus of Abdera (year 450 BC)

Importance of the model.

Although Democritus's model lacked experimental evidence and a solid scientific basis at the time, it laid the foundation for the idea that matter was composed of discrete, indivisible units. However, this model did not have an immediate impact on the scientific community of its time and was superseded by other ideas until it re-emerged with more force in the era of modern science.

Democritus's contribution is fundamental to the evolution of atomic theory throughout history, and his concept of the "atom" is the basis of how we understand the structure of matter today.

2. Model of John Dalton (1808)

The Dalton model of the atom, proposed by John Dalton in the early 19th century, was one of the first systematic attempts to explain the nature of matter and chemical reactions in terms of atoms.

Atoms as indivisible units

Atoms of different elements, conservation of mass, fixed proportions in compounds.

Dalton proposed the Law of Definite Proportions, which states that elements combine in fixed, constant proportions to form specific chemical compounds. This means that the atoms of the elements combine in simple whole numbers to form compounds.

Law of multiple proportions

3. thomson 's model (1904), model features, model limitations, 4. rutherford model (1911), discovery of the atomic nucleus, empty space in the atom, importance of the atomic model, 5. niels bohr 's atomic model (1913), discrete energy levels, absorption and emission of energy, atomic spectra, model limited to simple atoms, transitions and planck's constant, 6. schrödinger 's atomic model (1926), probabilistic description, schrödinger equation, orbitals and wave functions, heisenberg's uncertainty principle, evolution of quantum theory, 7. current atomic model (1926), fundamental particles, atomic nucleus, electrons and orbitals, quantum field theory.

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• Chemistry Matters

Unit 3: Atomic Structure

In this segment, the students learn about different models of the atom, including Dalton’s model, Thomson’s model, Rutherford’s model, and the Bohr model.

Georgia Standards of Excellence

Obtain, evaluate, and communicate information about the use of the modern atomic theory and periodic law to explain the characteristics of atoms and elements.

Evaluate merits and limitations of different models of the atom in relation to relative size, charge, and position of protons, neutrons, and electrons in the atom.

Obtain, evaluate, and communicate information from the Periodic Table to explain the relative properties of elements based on patterns of atomic structure.

Develop and use models to compare and contrast the structure of atoms, ions and isotopes.

• Number of valence electrons
• Types of ions formed by main group elements
• Location and properties of metals, nonmetals, and metalloids
• Phases at room temperature

Use the Periodic Table as a model to predict the above properties of main group elements.

Obtain, evaluate, and communicate information about the structure and properties of matter.

Develop models (e.g., atomic-level models, including drawings, and computer representations) by analyzing patterns within the periodic table that illustrate the structure, composition, and characteristics of atoms (protons, neutrons, and electrons) and simple molecules.

anion  - a negatively charged ion.

atomic number  - the number of protons in the nucleus of an atom.

atomic radius  - the distance from the atom's nucleus to the outermost energy level.

average atomic mass  - a weighted average of all of the isotopes of that element in the universe.

cation  - a positively charged ion.

effective nuclear charge (Zsubeff)  - the net positive charge experienced by the valence electrons from the nucleus.

electron  - a tiny particle with a negative charge that is found outside the nucleus of an atom.

electron configuration  - the order in which electrons are arranged in an atom.

electronegativity  - the ability of an atom to attract additional electrons.

energy sublevel  - a smaller part within a primary energy level.

excited state  - an atom, ion or molecule with an electron in a higher than normal energy level than its ground state.

ground state  - the lowest energy state within electron orbitals.

Hund's Rule  - When placing electrons in equal energy orbitals, electrons should not be paired until each equal energy orbital contains one electron.

ion  - an atom with a positive or negative charge.

ionization energy  - the amount of energy required to remove one valence electron from an atom.

isotope  - the same element with different numbers of neutrons.

model  - a physical, conceptual, or mathematical representation of a real phenomenon whose purpose is to explain and predict the observed phenomenon.

orbital  - a region of space around the nucleus of an atom where an electron is likely to be found.

Pauli exclusion principle  - when an orbital holds two electrons, the electrons much have opposite spin.

quantum  - a specific amount of energy that can be absorbed by an electron as it moves from ground state to excited state, or released by an electron as it falls from the excited state back to ground state.

subatomic - any smaller part of an atom such as a proton, neutron, or electron.

valence electrons  - electrons on the outer-most energy level of any atom.

valence shell  - the outer-most energy level of an electron. 

Teacher's Guide

The Chemistry Matters teacher toolkit provides instructions and answer keys for labs, experiments, and assignments for all 12 units of study. GPB offers the teacher toolkit at no cost to Georgia educators.  Complete and submit this form to request the teacher toolkit .  You only need to submit this form one time to get materials for all 12 units of study.

Support Materials

Chemistry matters segments.

Students analyze conceptual, mathematical, and physical models of atoms. This unit also includes an overview of protons, neutrons, and electrons, as well as a periodic table of elements.

Segment B: The Periodic Table

Segment C: Characteristics of Electrons

Segment D: Periodic Trends Part I

Segment E: Periodic Trends Part II

Segment F: Electron Configuration Part I

Segment G: Electron Configuration Part II

Segment H: Configuration Lab Results and Fireworks

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