1. The Development of Atomic Models
5.1
The Development of Atomic Models
Rutherford’s atomic model could not explain the chemical properties of elements.
Rutherford’s atomic model could not explain why objects change color when heated.
Rutherford’s model fails to explain why objects change color when heated. As the temperature of this horseshoe is increased, it first appears black, then red, then yellow, and then white. The observed behavior could be explained only if the atoms in the iron gave off light in specific amounts of energy. A better atomic model was needed to explain this observation. *

2. 5.1
The Bohr Model
Electrons are found only in specific circular paths, or orbits, around the nucleus. *

3. 5.1
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. *

4. 5.1
The Bohr Model
These ladder steps are somewhat like energy levels. In an ordinary ladder, the rungs are equally spaced. The energy levels in atoms are unequally spaced, like the rungs in this ladder. The higher energy levels are closer together. *

5. The Quantum Mechanical Model
5.1
The Quantum Mechanical Model
The Quantum Mechanical Model *

6. The Quantum Mechanical Model
5.1
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. *

7. The Quantum Mechanical Model
5.1
The Quantum Mechanical Model
The propeller blade has the same probability of being anywhere in the blurry region, but you cannot tell its location at any instant. The electron cloud of an atom can be compared to a spinning airplane propeller.
The electron cloud of an atom is compared here to photographs of a spinning airplane propeller. a) The airplane propeller is somewhere in the blurry region it produces in this picture, but the picture does not tell you its exact position at any instant. b) Similarly, the electron cloud of an atom represents the locations where an electron is likely to be found. *

8. The Quantum Mechanical Model
5.1
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 cloud. The cloud is more dense where the probability of finding the electron is high.
The electron cloud of an atom is compared here to photographs of a spinning airplane propeller. a) The airplane propeller is somewhere in the blurry region it produces in this picture, but the picture does not tell you its exact position at any instant. b) Similarly, the electron cloud of an atom represents the locations where an electron is likely to be found. *

9. Atomic Orbitals Atomic Orbitals
5.1
Atomic Orbitals
Atomic Orbitals
Principal Energy Level- signified by a number (1-7).
Each principal level has sublevels.
How do sublevels of principal energy levels differ? *

10. 5.1
Atomic Orbitals
An atomic orbital is often thought of as a region of space in which there is a high probability of finding an electron.
Each energy sublevel corresponds to an orbital of a different shape, which describes where the electron is likely to be found. *

11. 5.1
Atomic Orbitals
Different atomic orbitals are denoted by letters. The s orbitals are spherical, and p orbitals are dumbbell- shaped.
The electron clouds for the s orbital and the p orbitals are shown here. *

12. 5.1
Atomic Orbitals
Four of the five d orbitals have the same shape but different orientations in space.
The d orbitals are illustrated here. Four of the five d orbitals have the same shape but different orientations in space. Interpreting Diagrams How are the orientations of the dxy and dx2 – y2 orbitals similar? How are they different? *

14. 5.1
Atomic Orbitals
The numbers and kinds of atomic orbitals depend on the energy sublevel. *

15. 5.1
Atomic Orbitals
The number of electrons allowed in each of the first four energy levels are shown here. *

16. 1. Rutherford's planetary model of the atom could not explain
5.1 Section Quiz.
1. Rutherford's planetary model of the atom could not explain
any properties of elements.
the chemical properties of elements.
the distribution of mass in an atom.
the distribution of positive and negative charges in an atom. *

17. 2. Bohr's model of the atom proposed that electrons are found
5.1 Section Quiz.
2. Bohr's model of the atom proposed that electrons are found
embedded in a sphere of positive charge.
in fixed positions surrounding the nucleus.
in circular orbits at fixed distances from the nucleus.
orbiting the nucleus in a single fixed circular path. *

18. 5.1 Section Quiz.
3. What is the lowest-numbered principal energy level in which p orbitals are found? 1 2 3 4 *

19. END OF SHOW *