electron cloud atomic model

what are the chances

In the mid-1920s, an Austrian scientist named Erwin Schrdinger thought that the problem with Bohrs model was restricting the electrons to specific orbits. He wondered if electrons might behave like light, which scientists already knew had properties of both particles and waves. Schrdinger speculated that electrons might also travel in waves. Q: How do you pin down the location of an electron in a wave? A: You cant specify the exact location of an electron. However, Schrdinger showed that you can at least determine where an electron is most likely to be. Schrdinger developed an equation that could be used to calculate the chances of an electron being in any given place around the nucleus. Based on his calculations, he identified regions around the nucleus where electrons are most likely to be. He called these regions orbitals. As you can see in the Figure 1.2, orbitals may be shaped like spheres, dumbbells, or rings. In each case, the nucleus of the atom is at the center of the orbital.



where are the electrons

Up until about 1920, scientists accepted Niels Bohrs model of the atom. In this model, negative electrons circle the positive nucleus at fixed distances from the nucleus, called energy levels. You can see the model in Figure 1.1 for an atom of the element nitrogen. Bohrs model is useful for understanding properties of elements and their chemical interactions. However, it doesnt explain certain behaviors of electrons, except for those in the simplest atom, the hydrogen atom.

a fuzzy cloud

Schrdingers work on orbitals is the basis of the modern model of the atom, which scientists call the quantum mechanical model. The modern model is also commonly called the electron cloud model. Thats because each orbital around the nucleus of the atom resembles a fuzzy cloud around the nucleus, like the ones shown in the Figure 1.3 for a helium atom. The densest area of the cloud is where the electrons have the greatest chances of being. Q: In the model pictured in the Figure 1.3, where are the two helium electrons most likely to be? A: The two electrons are most likely to be inside the sphere closest to the nucleus where the cloud is darkest.


instructional diagrams

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orbitals may be shaped like

a) spheres.

b) dumbbells.

c) rings.

-->  d) all of the above

the atomic nucleus is always at the center of an orbital.

-->  a. true

b. false

schroedinger thought that electrons

a) are restricted to very specific orbits.

-->  b) might travel in waves like light.

c) have very precise locations.

d) behave like protons and neutrons.

bohrs atomic model explains all of the behaviors of electrons in atoms of all elements.

a. true

-->  b. false

the electron cloud model of the atom is no longer accepted by most scientists.

a. true

-->  b. false

diagram questions

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