Models of the Atom & Atomic Orbitals

1. Models of the Atom & Atomic Orbitals

2. 5.1 The Development of Atomic Models • The timeline shoes the development of atomic models from 1803 to 1911.

3. 5.1 The Development of Atomic Models • The timeline shows the development of atomic models from 1913 to 1932.

4. What was wrong with Rutherford’s Model? • Think back to Rutherford’s Gold foil experiment. • What did Rutherford say about the atom? • Atoms mostly empty space • Nucleus dense and positive • Electrons orbit the nucleus like planets orbit the sun • Rutherford’s model did not explain chemical properties of elements • His model also did not explain why objects change color when heated

5. Bohr’s Model • Bohr proposed that an electron is found only in specific circular paths, or orbits, around the nucleus. • 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.

6. 5.1 The Bohr Model • Like the rungs of the strange ladder, the energy levels in an atom are not equally spaced. • The higher the energy level occupied by an electron, the less energy it takes to move from that energy level to the next higher energy level.

7. Current atomic model- Quantum Mechanical Model • Still has the nucleus containing protons and neutrons in the center. • Still has electrons outside the nucleus in a low density area • 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. • This model is based on equations developed by Erwin Schrodinger

8. 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.

9. 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.

10. Principle Energy Levels of Electrons • Energy levels and # of electrons in each: • Level 1 Holds 2 • Level 2 Holds 8 • Level 3 Holds 18 • Level 4 Holds 32

11. Principle energy levels are broken down into sublevels called: 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. • Each orbital contains up to 2 electrons • Orbitals include: s, p, d, and f

12. 5.1 Atomic Orbitals • Different atomic orbitals are denoted by letters. The s orbitals are spherical, and p orbitals are dumbbell-shaped. • The s sublevel contains 1 orbital, so up to 2 electrons • The p sublevel contains 3 orbitals, so up to 6 electrons

13. 5.1 Atomic Orbitals • Four of the five d orbitals have the same shape but different orientations in space. • Since there are 5 orbitals, up to 10 electrons can be found in the d sublevel.

14. Atomic Orbitals • F orbitals. There are 7 with complex shapes. A few are shown below: • Since there are 7 orbitals, up to 14 electrons can be found in the f orbitals. • file:///C:/Chemistry%20PresentationExpress/Chapter05/Section01/ChemASAP/dswmedia/rsc/asap1_chem05_cman0505.html

15. Orbital Summary

16. Summary of Energy Levels and Orbitals

17. Periodic Table Showing Locations of some electrons The n represents the principle energy level The values for “n” are the same as the period numbers. Notice the s block has 2 columns because s can hold 2 electrons. The d block has 10 columns because d can hold up to 10 electrons The p block has 6 columns because p can hold up to 6 electrons