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
Chapter 11 Atoms, Energy and Electron Configurations Objectives 1. To review Rutherford’s model of the atom 2. To explore the nature of electromagnetic radiation 3. To see how atoms emit light Chapter 11 Atoms, Energy and Electron Configurations A. Rutherford’s Atom …….but there is a problem here!! Chapter 11 Atoms, Energy and Electron Configurations Using Rutherford’s Model Atoms Should Collapse…. …..then how are they so stable? Chapter 11 Atoms, Energy and Electron Configurations When were you last exposed to electromagnetic radiation? Chapter 11 Atoms, Energy and Electron Configurations B. Energy and Light • What is the nature of electromagnetic radiation? • How are the types of electromagnetic radiation different? – Light can be modeled as a wave, like a wave in water Chapter 11 Atoms, Energy and Electron Configurations B. Energy and Light • How are the types of light different? (m) ν( s-1) c = ν.λ – Wavelength, λ (Greek letter “lambda”) units - m – Frequency, ν (Greek letter “nu”) units - s-1 or Hertz (Hz) – Amplitude, peak height – relates to energy in wave – Speed, c : velocity of light in a vacuum is 3x108 m.s-1 Chapter 11 Atoms, Energy and Electron Configurations B. Energy and Light • Electromagnetic radiation Chapter 11 Atoms, Energy and Electron Configurations Wavelength and Frequency of Visible Light Frequency in Terahertz (1THz = 1012 Hz) and Wavelength in Nanometers (1nm = 10-9 meters) Chapter 11 Atoms, Energy and Electron Configurations Light Sometimes Behaves in Un-wavelike Ways • The Photoelectric Effect – Light shining on a metal surface can cause electrons to be separated from their atoms – Below a threshold frequency no electrons are emitted however high the intensity – At the threshold frequency electrons start to be emitted – At higher frequencies electrons have additional kinetic energy Photoelectric Effect Demo Chapter 11 Atoms, Energy and Electron Configurations B. Energy and Light • Dual nature of light – Two co-existing models – Wave – Photon – packet of energy Chapter 11 Atoms, Energy and Electron Configurations B. Energy and Light • Different photons (from light of different wavelengths) carry different amounts of energy. Energy of photon = h.ν (h is Planck’s Constant ) Chapter 11 Atoms, Energy and Electron Configurations C. Emission of Energy by Atoms • Atoms can give off light – They first must receive energy and become excited. – The energy is released in the form of a photon. Chapter 11 Atoms, Energy and Electron Configurations Typical Colors From Flame Tests K+ Na+ Periodic Table of Fireworks Li+ Which flame represents a higher energy transition? Cu2+ Chapter 11 Atoms, Energy and Electron Configurations Objectives 1. To understand how the emission spectrum of hydrogen demonstrates the quantized nature of energy 2. To learn about Bohr’s model of the hydrogen atom 3. To understand how the electron’s position is represented in the wave mechanical model Chapter 11 Atoms, Energy and Electron Configurations A. The Energy Levels of Hydrogen • Only certain types of photons are produced when excited Hydrogen atoms release energy. Why? Chapter 11 Atoms, Energy and Electron Configurations A. The Energy Levels of Hydrogen • Atomic states – Excited state – atom with excess energy – Ground state – atom in the lowest possible state • When an H atom absorbs energy from an outside source it enters an excited state. Chapter 11 Atoms, Energy and Electron Configurations A. The Energy Levels of Hydrogen • Energy level diagram • Energy in the photon corresponds to the energy used by the atom to get to the excited state. Chapter 11 Atoms, Energy and Electron Configurations A. The Energy Levels of Hydrogen • Only certain types of photons are produced when H atoms release energy. Why? Chapter 11 Atoms, Energy and Electron Configurations A. The Energy Levels of Hydrogen • Quantized Energy Levels – Since only certain energy changes occur the H atom must contain discrete energy levels. Chapter 11 Atoms, Energy and Electron Configurations B. The Niels Bohr Model of the Atom (1913-1915) • Bohr’s model of the atom – Quantized energy levels – Electron moves in a circular orbit – Electrons jump between levels by absorbing or emitting photons of a particular wavelength Able to mathematically explain the emission spectrum of Hydrogen (compare with Rutherford) Chapter 11 Atoms, Energy and Electron Configurations B. The Bohr Model of the Atom • Bohr’s model of the atom was not totally correct. – Had difficulties with spectra of larger atoms – Electrons do not move in a circular orbit and don’t seem to behave like discrete particles all the time Maybe small particles, such as electrons, can also behave like waves having a dual nature (just like photons)……? Chapter 11 Atoms, Energy and Electron Configurations C. The Wave Mechanical Model of the Atom (de Broglie and Schroedinger – mid-1920’s) • Orbitals – Nothing like orbits – Probability of finding the electron within a certain space BohrSchrodinger Chapter 11 Atoms, Energy and Electron Configurations Objectives 1. To learn about the shapes of the s, p and d orbitals 2. To review the energy levels and orbitals of the wave mechanical model of the atom 3. To learn about electron spin Chapter 11 Atoms, Energy and Electron Configurations A. The Hydrogen Orbitals • Orbitals do not have sharp boundaries. 90% boundary Chapter 11 Atoms, Energy and Electron Configurations A. The Hydrogen Orbitals Hydrogen Energy Levels • Hydrogen has discrete energy levels. • Called principal energy levels (electron shells) • Labeled with whole numbers • Energy is related to 1/n2 • En = E1/n2 • Energy levels are closer together the further they are from the nucleus Chapter 11 Atoms, Energy and Electron Configurations A. The Hydrogen Orbitals Hydrogen Energy Levels • Each principal energy level is divided into sublevels. – Labeled with numbers and letters – Indicate the shape of the orbital Chapter 11 Atoms, Energy and Electron Configurations Orbital Designations Chapter 11 Atoms, Energy and Electron Configurations Orbitals Define the Periodic Table “Orbitals” are “Energy Levels” Chapter 11 Atoms, Energy and Electron Configurations A. The Hydrogen Orbitals Hydrogen Energy Levels • The s and p types of sublevel Chapter 11 Atoms, Energy and Electron Configurations Representation of s, p, d atomic orbitals Chapter 11 Atoms, Energy and Electron Configurations A. The Hydrogen Orbitals Hydrogen Orbitals • Why does an H atom have so many orbitals and only 1 electron? – An orbital is a potential space for an electron. – Atoms can have many potential orbitals. • s, p, d, f orbitals named for sharp, principal, diffuse and fundamental lines on spectra. Further orbitals designated alphabetically Chapter 11 Atoms, Energy and Electron Configurations s p d d Orbitals f f f g g g g Chapter 11 Atoms, Energy and Electron Configurations B. The Wave Mechanical Model: Further Development Electron Spin • Close examination of spectra revealed doublets • Need one more property to determine how electrons are arranged • Spin – electron modeled as a spinning like a top • Spin is the basis of magnetism Chapter 11 Atoms, Energy and Electron Configurations B. The Wave Mechanical Model: Further Development Pauli Exclusion Principle • Pauli Exclusion Principle (Wolfgang Pauli 1925) - an atomic orbital can hold a maximum of 2 electrons and those 2 electrons must have opposite spins • When an orbital contains two electrons (of opposite spin) it is said to be full What are the four descriptors that define an energy level / electron’s position in an atom? Chapter 11 Atoms, Energy and Electron Configurations Objectives 1. To understand how the principal energy levels fill with electrons in atoms beyond hydrogen 2. To learn about valence electrons and core electrons 3. To learn about the electron configurations of atoms 4. To understand the general trends in properties in the periodic table Chapter 11 Atoms, Energy and Electron Configurations A. Electron Arrangements in the First 18 Atoms on the Periodic Table • H atom – Electron configuration – electron arrangement – 1s1 – Orbital diagram – orbital is represented as a box with a designation according to its sublevel. Contains arrow(s) to represent electrons (spin) Chapter 11 Atoms, Energy and Electron Configurations A. Electron Arrangements in the First 18 Atoms on the Periodic Table • He atom – Electron configuration – 1s2 – Orbital diagram Chapter 11 Atoms, Energy and Electron Configurations A. Electron Arrangements in the First 18 Atoms on the Periodic Table • Li atom – Electron configuration– 1s2 2s1 – Orbital diagram Write the electron configuration and orbital diagrams for Boron, Nitrogen, Fluorine and Argon Chapter 11 Atoms, Energy and Electron Configurations A. Electron Arrangements in the First 18 Atoms on the Periodic Table Write the full electron configuration of Neon and Sulfur Draw an orbital diagram for Magnesium and Chlorine Chapter 11 Atoms, Energy and Electron Configurations Order of Filling of Orbitals Atoms fill their orbitals in the order of their energies: Chapter 11 Atoms, Energy and Electron Configurations B. Electron Configurations and the Periodic Table • Orbital filling and the periodic table Dynamic Periodic Table PT 2a PT 2b Chapter 11 Atoms, Energy and Electron Configurations B. Electron Configurations and the Periodic Table • Electron configurations for K through Kr Chapter 11 Atoms, Energy and Electron Configurations B. Electron Configurations and the Periodic Table If there were more elements………. Chapter 11 Atoms, Energy and Electron Configurations A. Electron Arrangements in the First 18 Atoms on the Periodic Table Classifying Electrons • Valence electrons – electrons in the outermost (highest) principal energy level of an atom • Core electrons – inner electrons • Elements with the same valence electron arrangement (same group) show very similar chemical behavior. Chapter 11 Atoms, Energy and Electron Configurations B. Electron Configurations and the Periodic Table Chapter 11 Atoms, Energy and Electron Configurations Using a Noble Gas Shorthand • We can abbreviate electron configurations by using the configuration of the previous noble gas to cover the first part of the list of orbitals • Mg is 1s2 2s2 2p6 3s2 or [Ne] 3s2 • The noble gas portion is the equivalent to the group of core electrons • Use the Noble Gas shorthand to show the electron configurations of Carbon, Chlorine and Zirconium Chapter 11 Atoms, Energy and Electron Configurations C. Atomic Properties and the Periodic Table Metals and Nonmetals • Metals tend to lose electrons to form positive ions. • Nonmetals tend to gain electrons to form negative ions. Chapter 11 Atoms, Energy and Electron Configurations C. Atomic Properties and the Periodic Table Atomic Size • Size tends to increase down a column. • Size tends to decrease across a row. Effects of Shielding of outer electrons by inner orbitals (close to scale) Larger Chapter 11 Atoms, Energy and Electron Configurations C. Atomic Properties and the Periodic Table Ionization Energies • Ionization Energy – energy (ΔH) required to remove an electron from an individual atom (gas) – Tends to decrease down a column – Tends to increase across a row – Changes in an opposite direction to atomic size Chapter 11 Atoms, Energy and Electron Configurations Ionization Energies Chapter 11 Atoms, Energy and Electron Configurations Electron Affinity • Electron Affinity is defined as ΔH for the process: X(g) + e- = X(g)ΔH = Electron Affinity Larger Chapter 11 Atoms, Energy and Electron Configurations Electronegativity • Ionization Energy and Electron Affinity are combined to give Electronegativity – a measure of how well atoms compete for electrons in a bond Larger