Atomic Emission Spectra, & Electron Configuration. Unit 1 Coral Gables Senior High Ms. Kiely Pre-IB Chemistry I

Transcription

1 Atomic Emission Spectra, & Electron Configuration Unit 1 Coral Gables Senior High Ms. Kiely Pre-IB Chemistry I

2 Bell-Ringer What does Heisenberg s Uncertainty Principle state?

3 Answer Heisenberg s Uncertainty Principle: we cannot both know the position and the velocity of an electron. The best we can hope for is a probability picture of where the electron is likely to be.

4 Quiz Next Week Tues 9/25 Even, Weds 9/26 Odd Quiz is generally focused on: isotopes, mass number, relative atomic mass, electromagnetic radiation, the atomic emission spectra of hydrogen, ions, writing the ion charge on the chemical symbol of an ion, determining the amount of subatomic particles in neutral atoms as well as in ions, electron configuration of neutral atoms, electron configuration of ions

5 Textbook is online! The current lesson aligns most with Chapter 4 of your textbook.

6 IF BOHR S PLANETARY MODEL OF THE ATOM WAS WRONG, THEN WHAT DO WE BELIEVE TODAY ABOUT THE ATOM S STRUCTURE? -Based on Heisenberg s uncertainty principle, Erwin Schrödinger in 1926 developed a mathematical wave equation to figure out where an electron might be located within the electron cloud of an atom. -He knew that an electron s location within the electron cloud could not be known for certain- but a probability of where an electron might be could be calculated! -Schrödinger s wave equation is too complex to be considered here. However, each solution to the equation is known as a wave function, which is related to the probability of finding an electron within a particular volume of space around the nucleus. We call these spaces atomic orbitals.

7 These areas of space where the wave equation predicts electrons are located are three-dimensional regions around the nucleus called atomic orbitals. We can therefore say that atomic orbitals are regions around an atom s nucleus in which there is roughly a 90% probability of finding the electron. When electrons are in these atomic orbitals, they will move in specific directions. The direction of an electron s movement gives these orbitals their shapes. For example, the orbital that belongs to the sublevel for instance looks like a sphere because electrons move in a circular motion when they are occupied there.

8 Electron configuration chart: This chart helps us determine where electrons might be when at ground state! It is based off of Schrodinger s wave equations. Electron Configuration Diagram 1s_ 2s_ 2p _ 3s_ 3p _ 3d _ 4s_ 4p _ 4d _ 4f _ 5s_ 5p _ 5d _ 5f _ -Every number indicates an energy level in an atom. Only five energy levels are shown in this chart. -The letters (s, p, d, f) refer to the sublevels of orbitals that exist in an energy level. They also give insight into the motion of the electron and therefore the shape of the orbital. For example, the 1st level of an atom only has one sublevel, the s-sublevel, while the 4th energy level has four sublevels, the s, p, d, and f sublevels. -Each dash represents the amount of space each type of orbital has. Two electrons fit inside of each dash; i.e. the p-sublevel orbital can therefore hold up to 6 electrons.

9 How do we determine where electrons in an atom might be? Electron Configuration Rules 1. Aufbau Principle: lowest energy orbitals are filled first 2. Pauli Exclusion Principle: up to two electrons can occupy an orbital, however they must have opposite spins so as to reduce the repulsion of like charges. (Up arrow means clockwise, down arrow means counter-clockwise.) 3. Hund s Rule: electrons are placed into orbitals of a sublevel one electron at a time, so as to minimize the amount of repulsion in one given orbital. Once all orbitals in a sublevel are filled with one electron, then if more electrons remain a second electron with opposite spin can be added to completely fill the orbital. *Transition metals (metals located in groups 3-12) are exceptions to these rules. They will be addressed in an upcoming lecture.

10 Aufbau Principle

11 Practice 1. Using the diagram, determine the electron configuration of the following elements: Li, Mg, Ar, & K 2. State the full electron configuration of vanadium (V) and deduce the number of unpaired electrons.

12 Answers: 1. Li: 1s²2s Mg: 1s²2s²2p⁶3s² Ar: 1s²2s²2p⁶3s²3p⁶ K: 1s²2s²2p⁶3s²3p⁶4s 2. V: 1s²2s²2p⁶3s²3p⁶3d³4s² There are three unpaired electrons.

13 Practice Using the diagram, determine the electron configuration of the following elements: Ca, Ge, Rb, & C

14 Answers Ca: 1s²2s²2p⁶3s²3p⁶4s² Ge: 1s²2s²2p⁶3s²3p⁶3d¹⁰4s²4p² Rb: 1s²2s²2p⁶3s²3p⁶3d¹⁰4s²4p⁶5s¹ C: 1s²2s²2p²

15 Practice Which of the electron configuration rules are being broken in the following orbital diagram of oxygen?

16 Answer Which of the electron configuration rules are being broken in the following orbital diagram of oxygen? Pauli Exclusion principle Hund s Rule

17 NOBLE GAS CONFIGURATION Why are all the noble gases stable? The noble gases are all stable because they have completed the octet rule by having filled occupied sublevels in their outermost energy level (the valence energy level). This results in them having 8 valence electrons and the following electron configuration in their valence level: s²p⁶ (Except for Helium which only has s²) All atoms are trying to have noble gas electron configurations so that they can be stable! They will achieve this by becoming ions or bonding with other atoms.

18 THE OCTET RULE Octet Rule: Atoms tend to be stable when they are surrounded by 8 valence electrons. This ends up resulting in an electron configuration that ends with s²p⁶ Metal atoms will lose all their valence electrons in order to result in having a new outermost occupied valence level that will have 8 valence electrons. When this occurs, metal atoms become positive ions called cations. Nonmetal atoms will gain valence electrons until they have 8 valence electrons. When this happens, nonmetal atoms become negative ions called anions. Exceptions to the octet rule are Hydrogen and Helium, which only require 2 valence electrons to be stable. Another exception to the octet rule are the metals in groups 3-12 called Transition metals, which require 18 valence electrons to be stable; we will discuss these at a later time.

19 Electron Configuration of Ions Steps to determine the electron configuration of metal ions, cations: 1) solve for the electron configuration of the metal atom as if it was neutral 2) remove the valence electrons by removing the electrons that are located in the outermost occupied energy level. Make sure the new outermost occupied level only has 8 valence electrons. Steps to determine the electron configuration of nonmetal ions, anions: 1) solve for the electron configuration of the nonmetal atom as if it was neutral 2) add valence electrons to the outermost occupied energy level until the ion has a total of 8 valence electrons. (Unless it is Hydrogen, which is stable when it gains only one electron, giving it a total of two valence electrons).

20 Practice Write the full ground-state electron configuration of the following ions: 1) O² 2) Cl 3) Ca²+

21 Answers: 1) O² 1s²2s²2p⁶ 2) Cl 1s²2s²2p⁶3s²3p⁶ 3) Ca²+ 1s²2s²2p⁶3s²3p⁶

22 The electron configurations of the first 30 elements: