AP Chemistry Unit 3 - Elements

1. AP ChemistryUnit 3 - Elements Lesson 11 – Orbital Representations Book Section: 6.4-6.9

2. Orbital Diagrams • Each box in the diagram represents one orbital. • Half-arrows represent the electrons. • The direction of the arrow represents the relative spin of the electron.

3. Hund’s Rule • For degenerate orbitals, the lowest energy is attained when the number of electrons with the same spin is maximized. • Make all degenerate orbitals half-filled before adding the opposite spin electrons. • Half-filled subshells (p3, d5), are especially stable.

4. Magnetism • Magnetism results from unpaired electrons in the ground state. • When there are multiple unpaired electrons (like in iron), this results in a ferromagnet, or permanent magnet, or a paramagnet, or temporary magnet.

5. 1984 MC #66 • Ca, V, Co, Zn, As • Gaseous atoms of which of the following elements above are paramagnetic? • Ca and As • Zn and As • Ca, V, and Co • V, Co, and As • V, Co, and Zn

6. 1984 MC #66 • Ca, V, Co, Zn, As • Gaseous atoms of which of the following elements above are paramagnetic? • Ca and As • Zn and As • Ca, V, and Co • V, Co, and As – 42% correct, medium • V, Co, and Zn

7. 1994 MC #1-4 • Heisenberg uncertainty principle • Pauli exclusion principle • Hund’s rule (principle of maximum multiplicity) • Shielding effect • Wave nature of matter 1) Can be used to predict that a gaseous carbon atom in its ground state is paramagnetic. 2) Explains the experimental phenomenon of electron diffraction 3) Indicates that an atomic orbital can hold no more than two electrons 4) Predicts that it is impossible to determine simultaneously the exact position and exact velocity of an electron.

8. 1994 MC #1-4 • Heisenberg uncertainty principle • Pauli exclusion principle • Hund’s rule (principle of maximum multiplicity) • Shielding effect • Wave nature of matter 1) Can be used to predict that a gaseous carbon atom in its ground state is paramagnetic. C – 32% correct, hard 2) Explains the experimental phenomenon of electron diffraction E – 38% correct, hard 3) Indicates that an atomic orbital can hold no more than two electrons B - 44% correct, medium 4) Predicts that it is impossible to determine simultaneously the exact position and exact velocity of an electron., A – 82% correct, very easy

9. 1999 MC #5-8 • 1s ___ 2s ___ • 1s ___ 2s ___ • 1s ___ 2s ___ 2p ___ ___ ___ • 1s ___ 2s ___ 2p ___ ___ ___ • [Ar] 4s ___ 3d ___ ___ ___ ___ ___ 5) Represents an atom that is chemically unreactive 6) Represents an atom in an excited state 7) Represents an atom that has four valence electrons 8) Represents an atom of a transition metal

10. HW: 6.60, 62, 63, 64, 66 • Next Week: • Thursday– Periodic Trends • Friday – Radioactive Decay & Nuclear Equations • 10/18 – Gravimetric Analysis of a Chloride Salt Due • 10/20 – Elements Exam • 10/21 – Problem Set 2 Due