1. AP ChemistryUnit 3 - Elements Lesson 10 – Electron Configurations Book Section: 6.4-6.9

2. Electron Configurations • This shows the distribution of all electrons in an atom. • Each component consists of • A number denoting the energy level;

3. Electron Configurations • This shows the distribution of all electrons in an atom. • Each component consists of • A number denoting the energy level, • A letter denoting the type of orbital,

4. Electron Configurations • This shows the distribution of all electrons in an atom. • Each component consists of • A number denoting the energy level, • A letter denoting the type of orbital, • A superscript denoting the number of electrons in those orbitals.

5. Aufbau Principle • The order in which orbitals are filled with electrons is known as the Aufbau principle.

6. Full vs. Noble Gas Configuration • You can use a noble gas shell to shorten electron configurations. • Ex: Sodium • 1s22s22p63s1 • [Ne]3s1

7. Periodic Table • We fill orbitals in increasing order of energy. • Different blocks on the periodic table (shaded in different colors here) correspond to different types of orbitals.

8. Periodic Table • Some irregularities occur when there are enough electrons to half-fill s and d orbitals on a given row.

9. Periodic Table • For instance, the electron configuration for chromium is [Ar]4s13d5 rather than the expected [Ar]4s23d4. • Copper is [Ar]4s13d10.

10. Ionizing Transition Metals • When transition metals become ions, (Ex – Mn2+), the electrons are lost first from the s block, rather than the d block. • Electron configuration for Mn: [Ar]4s23d5 • Electron configuration for Mn+2: [Ar]3d5 • This is because the orbitals become “rearranged” once the electrons are put in them. (Crystal Field Theory & molecular orbitals – inorganic chemistry in college)

11. AP 1989 MC #4-7 • 1s22s22p53s23p5 • 1s22s22p63s23p6 • 1s22s22p62d103s23p6 • 1s22s22p63s23p63d5 • 1s22s22p63s23p63d34s2 4) An impossible electron configuration 5) The ground-state configuration for the atoms of a transition element 6) The ground-state configuration of a negative ion of a halogen 7) The ground-state configuration of a common ion of an alkaline earth element

12. AP 1989 MC #4-7 • 1s22s22p53s23p5 • 1s22s22p63s23p6 • 1s22s22p62d103s23p6 • 1s22s22p63s23p63d5 • 1s22s22p63s23p63d34s2 4) An impossible electron configuration – C (79% correct) - easy 5) The ground-state configuration for the atoms of a transition element – E (42% correct) - medium 6) The ground-state configuration of a negative ion of a halogen – B (62% correct) - easy 7) The ground-state configuration of a common ion of an alkaline earth element – B (40% correct) - medium

13. AP 1984 MC #22 1s22s22p63s23p3 Atoms of an element, X, have the electronic configuration shown above. The compound most likely formed with magnesium, Mg, is • MgX • Mg2X • MgX2 • MgX3 • Mg3X2

14. AP 1984 MC #22 1s22s22p63s23p3 Atoms of an element, X, have the electronic configuration shown above. The compound most likely formed with magnesium, Mg, is • MgX • Mg2X • MgX2 • MgX3 • Mg3X2 - 80% correct, very easy

15. AP 1984 MC #58 Which of the following represents the ground state electron configuration for the Mn3+ ion? (Atomic number Mn = 25) • 1s22s22p63s23p63d4 • 1s22s22p63s23p63d54s2 • 1s22s22p63s23p63d24s2 • 1s22s22p63s23p63d84s2 • 1s22s22p63s23p63d34s1

16. AP 1984 MC #58 Which of the following represents the ground state electron configuration for the Mn3+ ion? (Atomic number Mn = 25) • 1s22s22p63s23p63d4 – 32% correct - hard • 1s22s22p63s23p63d54s2 • 1s22s22p63s23p63d24s2 • 1s22s22p63s23p63d84s2 • 1s22s22p63s23p63d34s1

17. HW: 6.48, 50, 52, 54, 56, 58 • This Week: • Thursday – Gravimetric Analysis of a Chloride Salt, Quantitative Analysis of Soluble Sulfate Due • Friday – Electron Configurations (6.4-6.9) • 10/18 – Gravimetric Analysis of a Chloride Salt Due • 10/20 – Elements Exam • 10/21 – Problem Set 2 Due