TOPIC 2 ATOMIC STRUCTURE

1. TOPIC 2ATOMIC STRUCTURE 2.2 ELECTRON CONFIGURATION

2. ESSENTIAL IDEA The electron configuration of an atom can be deduced from its atomic number. NATURE OF SCIENCE (1.8) Developments in scientific research follow improvements in apparatus – the use of electricity and magnetism in Thomson’s cathode rays. NATURE OF SCIENCE (1.9) Theories being superseded – quantum mechanics is among the most current models of the atom. NATURE OF SCIENCE (2.2) Use theories to explain natural phenomena – line spectra explained by the Bohr model of the atom.

3. INTERNATIONAL-MINDEDNESS The European Organization for Nuclear Research (CERN) is run by its European member states (20 states in 2013), with involvement from scientists from many other countries. It operates the world’s largest particle physics research center, including particle accelerators and detectors used to study the fundamental constituents of matter.

4. THEORY OF KNOWLEDGE Heisenberg’s Uncertainty Principle states that there is a theoretical limit to the precision with which we can know the momentum and the position of a particle. What are the implications of this for the limits of human knowledge? “One aim of the physical sciences has been to give an exact picture of the material world. One achievement… has been to prove that this aim is unattainable.” – Jacob Bronowski. What are the implications of this claim for the aspirations of natural sciences in particular and for knowledge in general?

5. UNDERSTANDINGS/KEY IDEA2.2.A • Emission spectra are produced when photons are emitted from atoms as excited electrons return to a lower energy level.

6. APPLICATION/SKILLS • Be able to describe the relationship between color, wavelength, frequency and energy across the electromagnetic spectrum.

7. Describe the EM Spectrum • Electromagnetic radiation comes in different forms. • All forms travel at the same speed of light but have different wavelengths. • The higher energy forms have shorter wavelengths and higher frequencies.

8. ELECTROMAGNETIC SPECTRUM ORDER- lowest energy to highest • Radio waves • Microwaves • Infrared radiation • Visible light – ROYGBIV (lowest to highest) • Red<Orange<Yellow<Green<Blue<Indigo<Violet • Ultraviolet radiation • X rays • Gamma rays

9. APPLICATION/SKILLS • Distinguish between a continuous spectrum and a line spectrum.

10. CONTINUOUS SPECTRUM • A continuous spectrum is produced when white light is passed through a prism. • It shows all colors in an unbroken sequence of frequencies, such as the spectrum of visible light.

11. LINE SPECTRUM • A line spectrum is an emission spectrum that has sharp lines produced by specific frequencies of light. • It is produced by excited atoms and ions as they fall back to a lower energy level. • Different elements have different line spectra so they can be used to identify unknown elements.

12. GUIDANCE • The details of the electromagnetic spectrum are found in the data booklet in section 3.

13. UNDERSTANDINGS/KEY IDEA2.2.B • The line emission spectrum of hydrogen provides evidence for the existence of electrons in discrete energy levels, which converge at higher energies.

14. APPLICATION/SKILLS • Be able to describe the emission spectrum of the hydrogen atom, including the relationships between the lines and energy transitions to the first, second and third energy levels.

15. THE HYDROGEN SPECTRUM • The hydrogen atom gives out energy when an electron falls from a higher to a lower energy level. • Hydrogen produces visible light when an electron falls to the second energy level (n=2). • Transition to n=1 is a higher energy change and this is in the ultraviolet region of the spectrum. • When an electron falls to the 3rd or higher levels, infrared radiation is produced.

16. MORE HYDROGEN FACTS • When the energy levels are drawn around the nucleus, they are spaced farther apart near the nucleus and much closer together at higher energy levels. • If you had to draw the line spectrum for hydrogen, you would draw the lines closer together at higher energy. • The lines represent energy emitted when electrons falls from higher energy to lower energy levels.

17. www.astronomyknowhow.com

18. UNDERSTANDINGS/KEY IDEA2.2.C • The main energy level or shell is given an integer number, n, and can hold a maximum of electrons, 2n2.

19. UNDERSTANDINGS/KEY IDEA • A more detailed model of the atom describes the division of the main energy level into s, p, d, and f sub-levels of successively higher energies.

20. Energies of orbitals • Within an energy level, the “s” orbital has the lowest energy followed by “p”, then “d”, then “f” with the highest energy.

21. ORBITAL ENERGIES The Aufbau diagram shows us the energies of the various orbitals. The lowest energy is the 1s orbital. As you follow the arrows down, energy increases.

22. APPLICATION/SKILLS • Be able to recognize the shape of an “s” atomic orbital and the px, py and pz atomic orbitals.

23. s ORBITAL • The smallest orbital is the “s” orbital. The “s” orbital: • Has only 1 shape (holds 2 e-) • Is spherical in shape • Is the lowest energy orbital

24. p ORBITALS • The 2nd orbital shape is the “p” orbital shape. • There are 3 “p” shapes, each holding 2 electrons, for a total of 6 electrons in the “p” orbital. • The “p” orbitals are: • Dumbbell-shaped arranged at right angles with the nucleus at the center. • Higher in energy than the “s”

25. d ORBITALS • The 3rd orbital shape is the “d” orbital shape. • There are 5 “d” orbital shapes, for a total of 10 electrons in the “d” orbital. • “d” orbitals are higher in energy than “p” orbitals.

26. f ORBITALS • The last orbital shape is the “ f ” orbital shape. • “ f ” orbitals have irregular shapes due to quantum tunneling. • There are 7 “ f ” shapes, for a total of 14 electrons. • Electrons in f orbitals are very high in energy.

27. UNDERSTANDINGS/KEY IDEA2.2.E • Sub-levels contain a fixed number of orbitals, regions of space where there is a high probability of finding an electron.

28. Quantum Mechanical Model • The scientists Heisenberg, de Broglie and Schrodinger developed the current model of the atom called the Quantum Mechanical Model. • The electrons do not travel in precise orbits, but in wave functions called orbitals. • HEISENBERG UNCERTAINTY PRINCIPLE: • We are limited in just how precisely we can know both the position and momentum of a particle at a given time. • The wave function or orbital has a 90% probability of finding the electron within it.

29. State the maximum number of orbitals in a given energy level.

30. ORBITALS IN ENERGY LEVELS

31. Rules for electron configuration • To clarify, electron arrangement gives the number of electrons in each main energy level. • Electron configuration means the number of electrons in each sub-level.

32. APPLICATION/SKILLS • Be able to apply the Aufbau principle, Hund’s rule and the Pauli exclusion principle to write electron configurations for atoms and ions up to Z=36.

33. THREE MAIN RULES FOR e- CONFIG • Aufbau principle – electrons enter orbitals of lowest energy first • Pauli exclusion principle – an orbital can only hold 2 electrons with opposite spins. • Hund’s rule (Bus rule) – electrons enter orbitals singly until they have to pair up.

34. AUFBAU DIAGRAM • 1s 2s 2p 3s 3p 3d 4s 4p 4d 4f 5s 5p 5d 5f 5g 6s

35. GUIDANCE • You need to be able to write full or extended electron configurations as well as condensed or noble gas electron configurations.

36. WRITING ELECTRON CONFIG • If you are asked to write the extended or complete electron configuration, you must write it all out. • If not, you can use the shorthand or noble gas notation. • One other note, always write the n=3 sublevels before the n=4 when writing e- configuration. (First figure out the config using the Aufbau diagram, then write the levels in order.)

37. ELECTRON CONFIGURATION ON THE PERIODIC TABLE p orbitals s orbitals d orbitals (n-1) f orbitals (n-2)

38. GUIDANCE • The electron configuration exceptions of Cu and Cr should be known.

39. E- CONFIG EXCEPTIONS • There are 2 notable exceptions for electron configuration: • Chromium ends in 3d54s1, not 3d44s2 • Copper ends in 3d104s1, not 3d94s2 • The configuration is more stable filling each of the five “d” orbitals either singly or paired up, than filling the “s” orbital.

40. GUIDANCE • Be able to use orbital diagrams. www.chemistry.tutorvista.com www.study.com

41. UNDERSTANDINGS/KEY IDEA2.2.F • Each orbital has a defined energy state for a given electronic configuration and chemical environment and can hold two electrons of opposite spin.

42. The relative energy of the orbital depends on the atomic number. • The relative energies of the 4s and 3d orbitals is chemically significant. • The energy depends upon the attractions between the electrons and the nucleus and the inner-electron repulsions. • The 3d and 4s levels are very close in energy and they are very sensitive to inner-electron repulsions. • Transition elements will first lose the 4s electron to form ionsbefore they lose 3d electrons.

43. Deduce the electron arrangement for atoms and ions up to Z=20.

44. ELECTRON ARRANGEMENT • Valence electrons – outer shell electrons • Electron arrangement is a different notation from electron configuration. • Energy level 1: up to 2 • Energy level 2: up to 8 • Energy level 3: up to 8 • Energy level 4: end at 2

45. EXAMPLES • Lithium has 3 electrons with an arrangement of 2,1. • Aluminum has 13 electrons: 2, 8, 3 • Potassium has 19 electrons: 2, 8, 8, 1 • You must be able to use this notation for any element up to 20 electrons.

46. Citations International Baccalaureate Organization. Chemistry Guide, First assessment 2016. Updated 2015. Brown, Catrin, and Mike Ford. Higher Level Chemistry. 2nd ed. N.p.: Pearson Baccalaureate, 2014. Print. Most of the information found in this power point comes directly from this textbook. The power point has been made to directly complement the Higher Level Chemistry textbook by Catrin and Brown and is used for direct instructional purposes only.