Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Slide 1 ___________________________________ 10 Modern Atomic Theory and the Periodic Table ___________________________________ ___________________________________ ___________________________________ ___________________________________ ___________________________________ The amazing colors of fireworks result from electron transfer between energy levels of atoms. Foundations of College Chemistry, 14th Ed. ___________________________________ Morris Hein and Susan Arena Copyright © 2014 John Wiley & Sons, Inc. All rights reserved. Slide ___________________________________ Chapter Outline 2 • • • • • ___________________________________ 10.1 Electromagnetic Radiation 10.2 The Bohr Atom 10.3 Energy Levels of Electrons 10.4 Atomic Structure of the First 18 Elements 10.5 Electron Structures and the Periodic Table ___________________________________ ___________________________________ ___________________________________ ___________________________________ ___________________________________ © 2014 John Wiley & Sons, Inc. All rights reserved. Slide 3 ___________________________________ Electromagnetic Radiation ___________________________________ Electromagnetic Radiation: A form of energy that runs a continuum from radio to X-rays, visible light to microwaves. ___________________________________ Each form of radiation shares common characteristics: they display wavelike properties and travel at the same speed. ___________________________________ Basic Properties of Waves Wavelength (λ): the distance between consecutive peaks (or troughs) of a wave. ___________________________________ ___________________________________ Frequency ( ): the number of times a wave passes through a certain point per second. Speed: how fast a wave moves through space. © 2014 John Wiley & Sons, Inc. All rights reserved. ___________________________________ Slide 4 ___________________________________ Electromagnetic Radiation ___________________________________ Basic Properties of Waves ___________________________________ Wavelength (λ): the distance between consecutive peaks (or troughs) of a wave. ___________________________________ ___________________________________ ___________________________________ ___________________________________ © 2014 John Wiley & Sons, Inc. All rights reserved. Slide 5 ___________________________________ Electromagnetic Radiation ___________________________________ Electromagnetic Spectrum: The full range of electromagnetic radiation, arranged based on wavelength. ___________________________________ ___________________________________ ___________________________________ Electromagnetic radiation has both wave-like and particle properties. ___________________________________ Radiation can behave like tiny packets (“particles”) of energy called photons. ___________________________________ © 2014 John Wiley & Sons, Inc. All rights reserved. Slide 6 ___________________________________ The Bohr Atom At high temperatures or when high voltages are applied, elements radiate (emit) colored light. ___________________________________ When this light is passed through a prism, a set of brightly colored lines result. ___________________________________ ___________________________________ Line spectrum of hydrogen ___________________________________ These line spectra indicate the light emitted has only specific wavelengths/frequencies. ___________________________________ Each element possesses a characteristic and unique line spectrum. ___________________________________ © 2014 John Wiley & Sons, Inc. All rights reserved. Slide 7 ___________________________________ The Bohr Atom ___________________________________ How can these experimental results be explained? From his study of the line spectrum of hydrogen, Bohr proposed a revised theory of the atom. ___________________________________ ___________________________________ Bohr suggested electrons exist in specific regions at defined distances from the nucleus. ___________________________________ The electrons then move about the nucleus in circular orbits at a fixed distance from the nucleus. © 2014 John Wiley & Sons, Inc. All rights reserved. Slide 8 ___________________________________ ___________________________________ ___________________________________ The Bohr Atom ___________________________________ Bohr also suggested energy absorbed or emitted by an atom is quantized (has discrete fixed units). ___________________________________ Bohr proposed that electrons can orbit the nucleus at different distances. Each orbit is a distinct, discrete (quantized) energy level. ___________________________________ When an atom absorbs energy, the electrons can be promoted to higher energy levels. When an atom emits energy, the electrons can decays to a lower energy level. © 2014 John Wiley & Sons, Inc. All rights reserved. Slide 9 ___________________________________ ___________________________________ ___________________________________ ___________________________________ The Bohr Atom ___________________________________ Ground state: lowest energy level for an atom. ___________________________________ Each line in the spectrum corresponds to emission of energy as an electron relaxes from a higher to lower energy level. ___________________________________ Color of light emitted depends on the gap between the energy levels. ___________________________________ Bohr’s theory worked very well to explain and predict the line spectrum of hydrogen…. BUT…. ___________________________________ Bohr’s theory broke down in multi-electron systems. ___________________________________ © 2014 John Wiley & Sons, Inc. All rights reserved. Slide 10 ___________________________________ The Dual Particle/Wave Nature of Matter In 1924, DeBroglie (a French chemist) proposed matter could be treated as either a wave or a particle. ___________________________________ For large objects, the wave properties are negligible due to their very small wavelengths. ___________________________________ ___________________________________ For smaller objects with less mass, i.e. an electron, the wavelike properties of matter become very important. ___________________________________ Schrödinger in 1926 expanded the wavelike properties of matter by developing an equation to describe electrons as waves. ___________________________________ This theory, called quantum mechanics, allows one to calculate the probability of finding an electron in space. © 2014 John Wiley & Sons, Inc. All rights reserved. Slide 11 ___________________________________ ___________________________________ The Dual Particle/Wave Nature of Matter ___________________________________ Quantum mechanics deal in electron probabilities; orbits from Bohr theory are replaced by orbitals. ___________________________________ Orbitals: regions of space with a high probability of finding an electron. ___________________________________ ___________________________________ ___________________________________ ___________________________________ An orbital for a hydrogen atom. © 2014 John Wiley & Sons, Inc. All rights reserved. Slide 12 ___________________________________ Energy Levels of Electrons ___________________________________ Bohr’s idea of quantized energy levels does have parallels in quantum mechanics. ___________________________________ For example, quantum mechanics predicts discrete, quantized principal energy levels for electrons in an atom. ___________________________________ Principal energy level (n): provides a general idea of the distance of an electron from the nucleus (as n increases, so does the distance from the nucleus) ___________________________________ ___________________________________ ___________________________________ n can be a positive integer (1,2,3, etc.) © 2014 John Wiley & Sons, Inc. All rights reserved. Slide 13 ___________________________________ Energy Levels of Electrons ___________________________________ Each energy level can be divided into sublevels. Each sublevel corresponds to a different type of orbital that can house electrons. ___________________________________ Principal quantum level n =1 ___________________________________ Contains only one sublevel/orbital (1s orbital) ___________________________________ The orbital is spherical in nature, as are all s orbitals. ___________________________________ The orbital is a space where an electron has a 90% probability of being located. © 2014 John Wiley & Sons, Inc. All rights reserved. Slide 14 ___________________________________ ___________________________________ Energy Levels of Electrons ___________________________________ How many electrons can fit in an orbital? ___________________________________ Pauli Exclusion Principle: an atomic orbital can hold two electrons, which must have opposite spins. ___________________________________ Electron spin is represented by arrows ( or ) ___________________________________ ___________________________________ ___________________________________ © 2014 John Wiley & Sons, Inc. All rights reserved. Slide 15 ___________________________________ Energy Levels of Electrons Principal quantum level n =2 Contains two sublevels/orbitals (2s and 2p orbitals) ___________________________________ The 2s orbital is spherical like a 1s orbital, but larger and higher in energy. The 2p sublevel consists of three orbitals: px, py and pz. The shape of the 3 orbitals is the same; they differ in their orientation in space. ___________________________________ ___________________________________ ___________________________________ ___________________________________ 6 total electrons can occupy the 3 p orbitals of a subshell. Each p orbital has two lobes. © 2014 John Wiley & Sons, Inc. All rights reserved. ___________________________________ Slide ___________________________________ Energy Levels of Electrons 16 ___________________________________ Principal quantum level n =3 Contains three sublevels/orbitals (3s, 3p and 3d orbitals) ___________________________________ The 5 3d orbitals have unique shapes relative to s and p orbitals. ___________________________________ ___________________________________ ___________________________________ 10 total electrons can occupy the 5 d orbitals of a subshell. ___________________________________ © 2014 John Wiley & Sons, Inc. All rights reserved. Slide ___________________________________ Energy Levels of Electrons 17 With each new principal quantum level, a new sublevel/orbital type is introduced. ___________________________________ Quantum Level Summary ___________________________________ Sublevels Principal Quantum Level (n) 1 1s _____ _____ _____ 2 2s 2p 2p 2p _____ _____ 3 3s 3p 3p 3p 3d 3d 3d 3d 3d _____ 4 4s 4p 4p 4p 4d 4d 4d 4d 4d 4f 4f 4f 4f 4f 4f 4f ___________________________________ ___________________________________ ___________________________________ ___________________________________ © 2014 John Wiley & Sons, Inc. All rights reserved. Slide 18 ___________________________________ Energy Levels of Electrons Practice ___________________________________ What is the maximum number of electrons in a 4d sublevel? ___________________________________ ___________________________________ a. 2 b. 4 c. 6 Any d sublevel has 5 total orbitals. Two electrons can be housed in each orbital. ___________________________________ d. 10 ___________________________________ ___________________________________ © 2014 John Wiley & Sons, Inc. All rights reserved. Slide 19 ___________________________________ Energy Levels of Electrons Practice ___________________________________ What is the maximum number of electrons that can occupy the n = 3 sublevel? a. 8 b. 2 c. 18 d. 10 ___________________________________ ___________________________________ The n = 3 sublevel has 3 types of orbitals: s (1), p (3), and d (5). ___________________________________ Two electrons can occupy each orbital. (9 x 2 = 18) ___________________________________ ___________________________________ © 2014 John Wiley & Sons, Inc. All rights reserved. Slide 20 ___________________________________ Atomic Structure of the First 18 Elements ___________________________________ Hydrogen: consists of a nucleus with one proton and one electron in a 1s orbital. How are electrons treated in more complicated atoms that contain multiple electrons? Assuming multielectron atoms have orbitals similar to that of the hydrogen atom, rules for filling electrons can be developed. Guidelines for filling electrons: ___________________________________ ___________________________________ ___________________________________ 1. Only up to two electrons can occupy an orbital. 2. Electron will occupy lower energy orbitals first. Orbital energies: s < p < d < f for a given n value. 3. Each orbital in a sublevel must contain an electron before another electron can be added to any of the orbitals. © 2014 John Wiley & Sons, Inc. All rights reserved. Slide 21 ___________________________________ ___________________________________ ___________________________________ Atomic Structure of the First 18 Elements Three ways of depicting atomic and electronic structure: I) Atomic Structure Diagrams ___________________________________ Depict both the nuclear and electronic structure ___________________________________ ___________________________________ II) Electron configuration ___________________________________ Each orbital is listed, in order of increasing energy, while depicting the number of electrons in each orbital/sublevel. ___________________________________ ___________________________________ © 2014 John Wiley & Sons, Inc. All rights reserved. Slide 22 ___________________________________ Atomic Structure of the First 18 Elements ___________________________________ Three ways of depicting atomic and electronic structure: ___________________________________ III) Orbital Diagram Boxes represent orbitals and electron spins are represented as arrows. ___________________________________ ___________________________________ ___________________________________ 3p ___________________________________ © 2014 John Wiley & Sons, Inc. All rights reserved. Slide 23 ___________________________________ Atomic Structure of the First 18 Elements ___________________________________ Helium Hydrogen ___________________________________ 1s1 1s Orbital Diagram Electron configuration 1s2 1s Orbital Diagram Lithium ___________________________________ Berylium 2s 1s ___________________________________ 2s © 2014 John Wiley & Sons, Inc. All rights reserved. Slide 24 ___________________________________ 1s22s2 1s22s1 1s ___________________________________ Electron configuration ___________________________________ Atomic Structure of the First 18 Elements ___________________________________ Filling the p subshell Boron ___________________________________ 1s22s22p1 1s 2s ___________________________________ 2p Carbon ___________________________________ 1s22s22p2 ___________________________________ 1s 2s 2p Note the electrons are in different orbitals per Rule 3. The similar spin will be discussed shortly. © 2014 John Wiley & Sons, Inc. All rights reserved. ___________________________________ Slide 25 ___________________________________ Atomic Structure of the First 18 Elements ___________________________________ Filling the p subshell Nitrogen ___________________________________ 1s22s22p3 1s 2s ___________________________________ 2p Note the electrons are in different orbitals per Rule 3. ___________________________________ Oxygen ___________________________________ 1s22s22p4 1s 2s 2p ___________________________________ Two electrons must be paired in one p orbital. © 2014 John Wiley & Sons, Inc. All rights reserved. Slide 26 ___________________________________ Atomic Structure of the First 18 Elements ___________________________________ Filling the p subshell Fluorine ___________________________________ 1s22s22p5 1s 2s ___________________________________ 2p Neon ___________________________________ 1s22s22p6 1s 2s ___________________________________ 2p ___________________________________ All electrons are paired in the p shell. © 2014 John Wiley & Sons, Inc. All rights reserved. Slide 27 ___________________________________ Atomic Structure of the First 18 Elements ___________________________________ ___________________________________ ___________________________________ ___________________________________ ___________________________________ ___________________________________ © 2014 John Wiley & Sons, Inc. All rights reserved. Slide 28 ___________________________________ Atomic Structure of the First 18 Elements ___________________________________ Beyond Ne Sodium ___________________________________ 1s22s22p63s1 1s 2s 2p 3s ___________________________________ Begin filling the 3n shell. ___________________________________ ___________________________________ ___________________________________ © 2014 John Wiley & Sons, Inc. All rights reserved. Slide 29 ___________________________________ Atomic Structure of the First 18 Elements ___________________________________ Valence Electrons: electrons located in the highest energy (outermost) orbitals of an atom. Example Oxygen Electron configuration 1s22s22p4 ___________________________________ ___________________________________ Outermost valence electrons are in the n =2 subshell; oxygen has 6 total valence electrons. ___________________________________ The column number (1A-7A) in the periodic table gives the valence electrons of an element. ___________________________________ Valence electrons participate in bonding to form molecular compounds (see Chapter 11). ___________________________________ © 2014 John Wiley & Sons, Inc. All rights reserved. Slide ___________________________________ Electronic Configuration Practice 30 ___________________________________ How many valence electrons does phosphorus contain? ___________________________________ P is in Group 5A. It will contain 5 valence electrons. ___________________________________ c. 15 Electron Configuration 1s22s22p63s23p3 ___________________________________ d. 18 Valence electrons ___________________________________ a. 5 b. 8 ___________________________________ © 2014 John Wiley & Sons, Inc. All rights reserved. Slide 31 ___________________________________ Electronic Configuration Practice ___________________________________ Which element could have the following electron configuration? ___________________________________ 1s22s22p63s23p6 ___________________________________ a. Cl The element contains 18 electrons. It must also contain 18 protons. Atomic number 18 = argon. b. Ca c. Ar d. S ___________________________________ ___________________________________ ___________________________________ © 2014 John Wiley & Sons, Inc. All rights reserved. Slide 32 Electron Structures and the Periodic Table ___________________________________ How does the electronic structure of atoms relate to their positioning on the periodic table? ___________________________________ ___________________________________ ___________________________________ Origins of the Periodic Table ___________________________________ Mendeleev and Meyer proposed organizing elements based on increasing atomic masses. Their ideas formed the origins of the modern periodic table. ___________________________________ ___________________________________ © 2014 John Wiley & Sons, Inc. All rights reserved. Slide 33 ___________________________________ The Modern Periodic Table ___________________________________ columns (groups/families): ___________________________________ elements with similar properties. ___________________________________ rows (periods): ___________________________________ increasing Z ___________________________________ (atomic number) ___________________________________ © 2014 John Wiley & Sons, Inc. All rights reserved. Slide 34 ___________________________________ The Modern Periodic Table ___________________________________ ___________________________________ Period number corresponds to the highest principal quantum number n of the elements. ___________________________________ Group numbering: by numbers 1–18 or with numbers/letters (i.e., 7A). ___________________________________ A groups are the representative elements. ___________________________________ B groups are the transition elements. © 2014 John Wiley & Sons, Inc. All rights reserved. Slide 35 ___________________________________ ___________________________________ The Modern Periodic Table Main Group Alkali Metals Alkaline Earths ___________________________________ Noble Gases Halogens ___________________________________ Transition Metals ___________________________________ ___________________________________ ___________________________________ ___________________________________ Main Group © 2014 John Wiley & Sons, Inc. All rights reserved. Slide 36 ___________________________________ Periodic Table Practice ___________________________________ Magnesium is a member of what group of elements? ___________________________________ a. Halogens ___________________________________ b. Noble gases c. Alkali metals ___________________________________ d. Alkaline earth metals ___________________________________ ___________________________________ © 2014 John Wiley & Sons, Inc. All rights reserved. Slide 37 ___________________________________ The Modern Periodic Table ___________________________________ Group Commonalities: All elements in a group have similar valence electron configurations. This often leads to similar reactivity of elements in a group. Because electron configurations of larger elements are very long, a shorthand notation is used that highlights valence electrons. Example Na ___________________________________ ___________________________________ ___________________________________ [Ne]3s1 This indicates the electron configuration of sodium is that for Ne with an additional 3s1 electron. The shorthand electron configuration always uses the previous noble gas core with the valence electrons for the element of interest. © 2014 John Wiley & Sons, Inc. All rights reserved. Slide ___________________________________ ___________________________________ Initially, one may expect to fill 3d electrons before 4s electrons. ___________________________________ However, based on reactivity of the elements K and Ca, they resemble metals with valence electrons in s orbitals. ___________________________________ Example K Ca [Ar]4s1 [Ar]4s2 ___________________________________ Elements 21-30 are transition elements where electrons now fill in the 3d subshell. ___________________________________ Once the 3d subshell is filled, the 4p shell begins to fill. ___________________________________ © 2014 John Wiley & Sons, Inc. All rights reserved. 39 ___________________________________ Electron Filling 38 Slide ___________________________________ ___________________________________ Electron Filling ___________________________________ Sublevel Filling Diagram ___________________________________ ___________________________________ ___________________________________ ___________________________________ ___________________________________ © 2014 John Wiley & Sons, Inc. All rights reserved. Slide ___________________________________ Electron Filling Practice 40 ___________________________________ 4s1 The electron configuration [Ar] is the ground state electron configuration of: ___________________________________ ___________________________________ a. K b. P c. Fluorine The element contains 1 valence electron in the fourth period (due to n = 4). ___________________________________ d. Na ___________________________________ ___________________________________ © 2014 John Wiley & Sons, Inc. All rights reserved. Slide ___________________________________ Electron Filling Practice 41 ___________________________________ The electron configuration [Ne] 3s23p1, is the ground state electron configuration of: ___________________________________ ___________________________________ a. Na b. Al c. Ar The element contains 3 valence electrons in the third period (due to n = 3). ___________________________________ d. S ___________________________________ ___________________________________ © 2014 John Wiley & Sons, Inc. All rights reserved. Slide 42 ___________________________________ Chemical Periodicity ___________________________________ Groups of elements show similar chemical properties because of similarities in their valence electrons. ___________________________________ ___________________________________ ___________________________________ Group number equals the total number of outermost valence electrons. ___________________________________ Example Group 7 – contains the ns2np5 valence configuration ___________________________________ © 2014 John Wiley & Sons, Inc. All rights reserved. Slide 43 ___________________________________ Learning Objectives ___________________________________ 10.1 Electromagnetic Radiation ___________________________________ List the 3 basic characteristics of electromagnetic radiation ___________________________________ 10.2 The Bohr Atom Explain the relationship between the line spectrum and the quantized energy levels of an electron in an atom. ___________________________________ 10.3 Energy Levels of Electrons ___________________________________ Describe the principal energy levels, sublevels and orbitals of an atom. ___________________________________ © 2014 John Wiley & Sons, Inc. All rights reserved. Slide 44 ___________________________________ Learning Objectives ___________________________________ 10.4 Atomic Structure of the First 18 Elements ___________________________________ Use the guidelines to write electron configurations. ___________________________________ 10.5 Electron Structures and the Periodic Table ___________________________________ Describe how the electron configurations of the atoms relate to their position on the periodic table and write electron configurations for elements based on their position on the periodic table. © 2014 John Wiley & Sons, Inc. All rights reserved. ___________________________________ ___________________________________