1. Chapter 5 Electrons In Atoms 5.1 Revising the Atomic Model
5.2 Electron Arrangement in Atoms
5.3 Atomic Emission Spectra and
the Quantum Mechanical Model
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2. CHEMISTRY & YOU
Why do scientists use mathematical models to describe the position of electrons in atoms?
Shown here is a life-sized model of a skier, but not all models are physical. In fact, the current model of the atom is a mathematical model.
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3. What did Bohr propose in his model of the atom?
Energy Levels in Atoms
Energy Levels in Atoms
What did Bohr propose in his model of the atom?
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4. Limitations of Rutherford’s Atomic Model
Energy Levels in Atoms
Limitations of Rutherford’s Atomic Model
It explained only a few simple properties of atoms.
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5. Limitations of Rutherford’s Atomic Model
Energy Levels in Atoms
Limitations of Rutherford’s Atomic Model
It explained only a few simple properties of atoms.
It could not explain the chemical properties of elements.
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6. Limitations of Rutherford’s Atomic Model
Energy Levels in Atoms
Limitations of Rutherford’s Atomic Model
It explained only a few simple properties of atoms.
It could not explain the chemical properties of elements.
For example, Rutherford’s model could not explain why an object such as the iron scroll shown here first glows dull red, then yellow, and then white when heated to higher and higher temperatures.
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7. Energy Levels in Atoms
The Bohr Model
In 1913, Niels Bohr (1885–1962), a young Danish physicist and a student of Rutherford, developed a new atomic model.
He changed Rutherford’s model to incorporate newer discoveries about how the energy of an atom changes when the atom absorbs or emits light.
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8. Energy Levels in Atoms
The Bohr Model
Bohr proposed that an electron is found only in specific circular paths, or orbits, around the nucleus.
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9. Each possible electron orbit in Bohr’s model has a fixed energy.
Energy Levels in Atoms
The Bohr Model
Each possible electron orbit in Bohr’s model has a fixed energy.
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10. Each possible electron orbit in Bohr’s model has a fixed energy.
Energy Levels in Atoms
The Bohr Model
Each possible electron orbit in Bohr’s model has a fixed energy.
The fixed energies an electron can have are called energy levels.
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11. Each possible electron orbit in Bohr’s model has a fixed energy.
Energy Levels in Atoms
The Bohr Model
Each possible electron orbit in Bohr’s model has a fixed energy.
The fixed energies an electron can have are called energy levels.
A quantum of energy is the amount of energy required to move an electron from one energy level to another energy level.
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12. Energy Levels in Atoms
The Bohr Model
The rungs on this ladder are somewhat like the energy levels in Bohr’s model of the atom.
A person on a ladder cannot stand between the rungs. Similarly, the electrons in an atom cannot exist between energy levels.
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13. Energy Levels in Atoms
The Bohr Model
The rungs on this ladder are somewhat like the energy levels in Bohr’s model of the atom.
The energy levels in atoms are unequally spaced, like the rungs in this unusual ladder. The higher energy levels are closer together.
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14. How does the Bohr model improve upon the Rutherford model?
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15. How does the Bohr model improve upon the Rutherford model?
The Rutherford model could not explain why elements that have been heated to higher and higher temperatures give off different colors of light. The Bohr model explains how the energy levels of electrons in an atom change when the atom emits light.
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16. The Quantum Mechanical Model
What does the quantum mechanical model determine about the electrons in an atom?
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17. The Quantum Mechanical Model
Austrian physicist Erwin Schrödinger (1887–1961) used new theoretical calculations and experimental results to devise and solve a mathematical equation describing the behavior of the electron in a hydrogen atom.
The modern description of the electrons in atoms, the quantum mechanical model, came from the mathematical solutions to the Schrödinger equation.
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18. The Quantum Mechanical Model
Like the Bohr model, the quantum mechanical model of the atom restricts the energy of electrons to certain values.
Unlike the Bohr model, however, the quantum mechanical model does not specify an exact path the electron takes around the nucleus.
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19. The Quantum Mechanical Model
The quantum mechanical model determines the allowed energies an electron can have and how likely it is to find the electron in various locations around the nucleus of an atom.
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20. The Quantum Mechanical Model
Probability describes how likely it is to find an electron in a particular location around the nucleus of an atom.
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21. The Quantum Mechanical Model
In the quantum mechanical model, the probability of finding an electron within a certain volume of space surrounding the nucleus can be represented as a fuzzy cloudlike region.
The cloud is more dense where the probability of finding the electron is high.
Electron cloud
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22. How are the quantum mechanical model and the Bohr model alike
How are the quantum mechanical model and the Bohr model alike? How are they different?
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23. How are the quantum mechanical model and the Bohr model alike
How are the quantum mechanical model and the Bohr model alike? How are they different?
Like the Bohr model, the quantum mechanical model restricts the energy of electrons to certain values. Unlike the Bohr model, the quantum mechanical model does not specify an exact path the electron takes around the nucleus.
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24. How do sublevels of principal energy levels differ?
Atomic Orbitals
Atomic Orbitals
How do sublevels of principal energy levels differ?
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25. Atomic Orbitals
Solutions to the Schrödinger equation give the energies, or energy levels, an electron can have.
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26. Atomic Orbitals
Solutions to the Schrödinger equation give the energies, or energy levels, an electron can have.
For each energy level, the Schrödinger equation also leads to a mathematical expression, called an atomic orbital.
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27. Atomic Orbitals
Solutions to the Schrödinger equation give the energies, or energy levels, an electron can have.
For each energy level, the Schrödinger equation also leads to a mathematical expression, called an atomic orbital.
An atomic orbital is represented pictorially as a region of space in which there is a high probability of finding an electron.
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28. Atomic Orbitals
The energy levels of electrons in the quantum mechanical model are labeled by principal quantum numbers (n).
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29. These numbers are assigned the values n = 1, 2, 3, 4, and so forth.
Atomic Orbitals
The energy levels of electrons in the quantum mechanical model are labeled by principal quantum numbers (n).
These numbers are assigned the values n = 1, 2, 3, 4, and so forth.
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30. These numbers are assigned the values n = 1, 2, 3, 4, and so forth.
Atomic Orbitals
The energy levels of electrons in the quantum mechanical model are labeled by principal quantum numbers (n).
These numbers are assigned the values n = 1, 2, 3, 4, and so forth.
For each principal energy level greater than 1, there are several orbitals with different shapes and at different energy levels.
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31. These numbers are assigned the values n = 1, 2, 3, 4, and so forth.
Atomic Orbitals
The energy levels of electrons in the quantum mechanical model are labeled by principal quantum numbers (n).
These numbers are assigned the values n = 1, 2, 3, 4, and so forth.
For each principal energy level greater than 1, there are several orbitals with different shapes and at different energy levels.
These energy levels within a principal energy level constitute energy sublevels.
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32. Atomic Orbitals
Each energy sublevel corresponds to one or more orbitals of different shapes. The orbitals describe where an electron is likely to be found.
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33. Different atomic orbitals are denoted by letters.
The s orbitals are spherical.
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34. Different atomic orbitals are denoted by letters.
The s orbitals are spherical.
The p orbitals are dumbbell-shaped.
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35. Atomic Orbitals
For a given principal energy level greater than 1, there is one s orbital…
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36. Atomic Orbitals
For a given principal energy level greater than 1, there is one s orbital, 3 p orbitals...
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37. Atomic Orbitals
For a given principal energy level greater than 1, there is one s orbital, 3 p orbitals, and 5 d orbitals.
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38. Atomic Orbitals
Four of the five d orbitals have the same shape but different orientations in space.
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39. Atomic Orbitals
The numbers and types of atomic orbitals depend on the principal energy level.
Summary of Principal Energy Levels and Sublevels
Principal energy level
Number of sublevels
Type of sublevel
Maximum number of electrons
n = 1 1
1s (1 orbital) 2
n = 2
2s (1 orbital), 2p (3 orbitals) 8
n = 3 3
3s (1 orbital), 3p (3 orbitals),
3d (5 orbitals) 18
n = 4 4
4s (1 orbital), 4p (3 orbitals),
4d (5 orbitals), 4f (7 orbitals) 32
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40. Atomic Orbitals
The principal quantum number, n, always equals the number of sublevels within that principal energy level.
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41. The number of orbitals in a principal energy level is equal to n2.
Atomic Orbitals
The principal quantum number, n, always equals the number of sublevels within that principal energy level.
The number of orbitals in a principal energy level is equal to n2.
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42. The number of orbitals in a principal energy level is equal to n2.
Atomic Orbitals
The principal quantum number, n, always equals the number of sublevels within that principal energy level.
The number of orbitals in a principal energy level is equal to n2.
A maximum of two electrons can occupy an orbital.
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43. The number of orbitals in a principal energy level is equal to n2.
Atomic Orbitals
The principal quantum number, n, always equals the number of sublevels within that principal energy level.
The number of orbitals in a principal energy level is equal to n2.
A maximum of two electrons can occupy an orbital.
Therefore, the maximum number of electrons that can occupy a principal energy level is given by the formula 2n2.
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44. Calculate the maximum number of electrons in the 5th principal energy level (n = 5).
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45. Calculate the maximum number of electrons in the 5th principal energy level (n = 5).
The maximum number of electrons that can occupy a principal energy level is given by the formula 2n2. If n = 5, 2n2 = 50.
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46. CHEMISTRY & YOU
Why do scientists no longer use physical models to describe the motion of electrons?
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47. CHEMISTRY & YOU
Why do scientists no longer use physical models to describe the motion of electrons?
Previous models of the atom were physical models based on the motion of large objects.
Theoretical calculations and experimental results showed that these models did not always correctly describe electron motion.
Schrödinger devised a mathematical equation describing the behavior of the electron in a hydrogen atom. The quantum mechanical model came from the solutions to the Schrödinger equation.
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48. Key Concepts
Bohr proposed that an electron is found only in specific circular paths, or orbits, around the nucleus.
The quantum mechanical model determines the allowed energies an electron can have and how likely it is to find the electron in various locations around the nucleus of an atom.
Each energy sublevel corresponds to one or more orbitals of different shapes, which describe where the electron is likely to be found.
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49. Glossary Terms
energy level: the specific energies an electron in an atom or other system can have
quantum: the amount of energy needed to move an electron from one energy level to another
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50. Glossary Terms
quantum mechanical model: the modern description, primarily mathematical, of the behavior of electrons in atoms
atomic orbital: a mathematical expression describing the probability of finding an electron at various locations; usually represented by the region of space around the nucleus where there is a high probability of finding an electron
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51. Electrons and the Structure of Atoms
BIG IDEA
Electrons and the Structure of Atoms
The quantum mechanical model of the atom comes from the solutions to the Schrödinger equation.
Solutions to the Schrödinger equation give the energies an electron can have and the atomic orbitals, which describe the regions of space where an electron may be found.
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52. END OF 5.1
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