What is the Modern Atomic Theory?

Joseph Comunale, Rebecca Gillaspy
  • Author
    Joseph Comunale

    Joseph Comunale obtained a Bachelor's in Philosophy from UCF before becoming a high school science teacher for five years. He has taught Earth-Space Science and Integrated Science at a Title 1 School in Florida and has Professional Teacher's Certification for Earth-Space Science.

  • Instructor
    Rebecca Gillaspy

    Dr. Gillaspy has taught health science at University of Phoenix and Ashford University and has a degree from Palmer College of Chiropractic.

Learn about the modern atomic model. Understand the modern atomic theory and Schrodinger model. Discover what the modern atomic model is called, i.e., "electron cloud." Updated: 11/09/2021

Table of Contents


Modern Atomic Theory

Modern atomic theory refers to the most current or paradigm theory of atoms. Modern atomic theory is the best explanation atomic physicists have for how atoms look and behave. The basics of the atomic theory are that atoms are the smallest units of chemical matter. Elements are the simplest chemical substances that cannot chemically break down any further. Each element is made up of its own atoms, different from atoms of all other elements. However, atoms can break down further into subatomic particles. Each element is made up of atoms that all have the same number of protons, a positively charged subatomic particle within the atom's nucleus. Additionally, the nucleus contains neutrons, but sometimes in varying numbers between isotopes of the same type of atom. Isotopes are atoms that have the same number of protons but different numbers of neutrons. For example, all hydrogen atoms have one proton, but there is more than one isotope of hydrogen; hydrogen-1 has no neutrons, and hydrogen-2 has one neutron.

Additionally, negatively charged quanta electrons are electrostatically attracted to the positively charged nucleus and therefore surround it. Many simple models of the atom show electrons as particles or spheres that orbit the nucleus like planets orbit suns. However, this representation doesn't provide the most accurate or honest picture of the actual nature of electrons. The modern atomic model instead describes electrons as cloud-like, waves, probability functions, or even undecidable.

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Modern Atomic Model

The modern atomic model represents atoms containing a nucleus of protons and neutrons and a vague gradient or cloud surrounding it containing the electrons; this is sometimes referred to as the cloud model. The reason electrons are represented as a cloud is because of their behavior being probabilistic. According to experiments done by atomic physicists, electrons behave in a way that makes it impossible to measure both their position and momentum simultaneously. This behavior is wave-like.

This diagram shows an interference pattern.

This image shows a interference pattern. This is what is projected on a surface when light passes through two close, tiny, parallel slits.

Electrons aren't the only things that behave in this strange manner. For the longest time, scientists and philosophers debated the nature of light: was it a wave or a particle. The debate was partially settled when an experiment performed by Thomas Young showed that light behaves as a wave. Young set up an experiment where the light shined through two tiny parallel slits before being emitted onto a surface. When monochromatic light such as a laser passes through two slits, it projects an interference pattern on the surface to which it is cast. This pattern appears as dots or lines that run parallel, with no light in between them, and fade out from a concentrated center.

This diagram shows the basics of the double-slit experiment. Light passing through two slits interferes with itself and creates an interference pattern where areas of the light have been canceled out.

What is the modern atomic theory and the modern atomic model is in large part due to the wave-like properties of some particles.

This gif shows how ripples or waves from two sources interfere with each other. Light behaves in this way when passing through two slits.

This gif shows how ripples or waves from two sources interfere with each other.

Thomas young's double-slit experiment demonstrates the wave-like nature of light. As the light passes through two slits, the light propagating from each slit interferes with the light from the other slit. As the light spreads out and intersects itself, it interferes with itself, either constructively or destructively; this is how two sets of propagating waves or ripples behave in still water. When the peak of one wave meets the peak of another wave, they constructively interfere with each other and maintain the wave peak. However, when the peak of one wave meets with the trough or valley of another wave, the waves cancel each other out, and the water's surface goes flat. In the case of light propagating from two slits, the light waves cancel each other out and result in the interference pattern. The areas on the surface the light projects on are dark and lack light if the waves destructively interfere with each other.

After Thomas Young demonstrated light was wave-like, George Paget Thomson attempted a similar experiment using beams of electrons. Electrons, too, were discovered to be wave-like and created interference patterns.

This diagram shows how electrons fired through two slits also demonstrate wave-like properties and result in an interference pattern.

Schrodinger and Heisenberg developed their model of the atom, the Schrodinger model or modern cloud theory model after the electron was discovered to have wave-like properties.

Two more physicists named Erwin Schrodinger and Werner Heisenberg contributed further to the study of quantum mechanics or the nature of subatomic particles. Heisenberg, with other physicists, proposed that this strange probabilistic nature of quantum mechanics was not some momentary obstacle scientists faced before they could determine the true position and momentum of something like electrons. Instead, this non-deterministic nature was the way things behaved at the quantum level. Schrodinger eventually provided a wave equation for electrons which described how they propagate. Because electrons travel or propagate as waves, they don't have an exact position. Therefore, their position and momentum or speed cannot be determined at the same time. This position is known as Heisenberg's uncertainty principle which asserts some mathematical inequalities exist where there is a limit to the accuracy for determining and predicting pairs of physical quantities based on initial conditions. The accuracy in determining one aspect reduces the accuracy of determining another aspect; this is simply the nature of electrons; they are probabilistic functions and not deterministic particles.

Though this sounds confusing, it must be understood that the very nature of all human language is that it developed and evolved by being utilized to describe and explain things and phenomena at a macroscopic scale, or the familiar physical world observed in everyday life, and not the things in the quantum world. Therefore, though it seems counterintuitive for an electron to be in two places at once or interfere with itself, the quantum world is under no obligation to be intuitive and compatible with a macroscopic human language.

This diagram demonstrates the uncertainty principle. The more accurately one measures an electron position, the less accurate the momentum prediction becomes.

This diagram demonstrates Heisenberg Uncertainty Principle.

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Frequently Asked Questions

What is Schrödinger's atomic model?

The Erwin Schrödinger model of the atom is composed of the nucleus of the atom which contains protons and neutrons and is surrounded by an electron cloud. This is sometimes called the cloud model. Electrons exist in a "cloud" because they have a probabilistic nature and it is impossible to simultaneously know their position and their momentum.

Who proposed the modern atomic model?

The modern atomic model is the culmination of experiments and research done by a few scientists. Werner Heisenberg and Erwin Schrodinger are most credited for discovering the probabilistic nature of the electron and applying it to the model of the atom. They represented the atom as a nucleus with protons and neutrons, surrounded by a cloud of electrons.

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