1. Chapter 5 Periodicity and Atomic Structure

3. 5.1 Development of Periodic Table A.Creation of the Periodic table A.Creation of the Periodic table 1.Ideal example of how scientific theory comes into being 1.Ideal example of how scientific theory comes into being 2.Random observation 2.Random observation 3.Organization of data in ways that make sense 3.Organization of data in ways that make sense 4.Consistent hypothesis emerges 4.Consistent hypothesis emerges 5.Explains known facts 5.Explains known facts 6.Makes predictions about unknown phenomena 6.Makes predictions about unknown phenomena

4. 5.1 Periodic Table Con’t B.Mendelee's hypothesis about organizing known chemical information B.Mendelee's hypothesis about organizing known chemical information 1.Met criteria for a good hypothesis 1.Met criteria for a good hypothesis 2.Listed the known elements by atomic weight 2.Listed the known elements by atomic weight 3.Grouped them together according to their chemical reactivity 3.Grouped them together according to their chemical reactivity 4.was able to predict the properties of unknown elements – eka – aluminum, eka – silicon 4.was able to predict the properties of unknown elements – eka – aluminum, eka – silicon

5. The Early Periodic Table

7. 5.2 Electromagnetic Radiation Electromagnetic radiation – forms of radiant energy (light in all its varied forms) Electromagnetic radiation – forms of radiant energy (light in all its varied forms) Electromagnetic spectrum – a continuous range of wavelengths and frequencies of all forms of electromagnetic radiation Electromagnetic spectrum – a continuous range of wavelengths and frequencies of all forms of electromagnetic radiation

8. 5.2 Electromagnetic Radiation Radiation energy – has wavelike properties Radiation energy – has wavelike properties Frequency (ν, Greek nu) – the number of peaks (maxima) that pass by a fixed point per unit time (s-1 or Hz) Frequency (ν, Greek nu) – the number of peaks (maxima) that pass by a fixed point per unit time (s-1 or Hz) Wavelength (λ, Greek lambda) – the length from one wave maximum to the next Wavelength (λ, Greek lambda) – the length from one wave maximum to the next Amplitude – the height measured from the middle point between peak and trough (maximum and minimum) Amplitude – the height measured from the middle point between peak and trough (maximum and minimum) Intensity of radiant energy is proportional to amplitude Intensity of radiant energy is proportional to amplitude

9. Electromagnetic Waves

10. Speed of Light Speed of light (c) – rate of travel of all electromagnetic radiation in a vacuum Speed of light (c) – rate of travel of all electromagnetic radiation in a vacuum c = 3.00 x 10 8 m/s c = 3.00 x 10 8 m/s Wavelength x Frequency = Speed Wavelength x Frequency = Speed c = λν Frequency and wavelength are inversely related Frequency and wavelength are inversely related long λ  low ν (nu) long λ  low ν (nu) short λ  high v (nu) short λ  high v (nu)

11. Example Calculate the wavelength, in meters, of radiation with a frequency of 4.62 x 10 14 s -1. What region of the electromagnetic spectrum is this? Calculate the wavelength, in meters, of radiation with a frequency of 4.62 x 10 14 s -1. What region of the electromagnetic spectrum is this?

12. Example

15. 5.3– Electromagnetic Radiation and Atomic Spectra Individual atoms give off light when heated or otherwise excited energetically Individual atoms give off light when heated or otherwise excited energetically Provides clue to atomic makeup Provides clue to atomic makeup Consists of only few λ Consists of only few λ Line spectrum – series of discrete lines ( or wavelengths) separated by blank areas Line spectrum – series of discrete lines ( or wavelengths) separated by blank areas E.g. Lyman series in the ultraviolet region E.g. Lyman series in the ultraviolet region

16. The energy level of Hydrogen

17. 1.– Particlelike Properties of Electromagnetic Radiation: The Planck Equation

18. Emission of Energy by Atom How does atom emit light? How does atom emit light? Atoms absorbs energy Atoms absorbs energy Atoms become excited Atoms become excited Release energy Release energy Higher-energy photon –>shorter wavelength Higher-energy photon –>shorter wavelength Lower-energy photon -> longer wavelength Lower-energy photon -> longer wavelength

19. 5.4 – Particlelike Properties of Electromagnetic Radiation: The Planck Equation Blackbody radiation – the visible glow that solid objects give off when heated Blackbody radiation – the visible glow that solid objects give off when heated Intensity does not continue to rise indefinitely as λ decreases Intensity does not continue to rise indefinitely as λ decreases – the dependence of the intensity of blackbody radiation on wavelength at different temperature – the dependence of the intensity of blackbody radiation on wavelength at different temperature

20. Planck Equation Planck – energy radiated by a heated object is quantized Planck – energy radiated by a heated object is quantized Radiant energy emitted in discrete units or quanta Radiant energy emitted in discrete units or quanta The smallest quantity of energy that can be emitted in the form of electromagnetic radiation The smallest quantity of energy that can be emitted in the form of electromagnetic radiation E = hν or E = hν or h = 6.626 x 10 -34 Js (Planck’s constant) h = 6.626 x 10 -34 Js (Planck’s constant) unit of E is J/proton unit of E is J/proton high energy radiation – higher ν, shorter λ high energy radiation – higher ν, shorter λ low energy radiation – lower ν, higher λ low energy radiation – lower ν, higher λ

21. Black Body Radiation

22. Examples What is the energy (kJ/mol) of photons of radar wave with What is the energy (kJ/mol) of photons of radar wave with ν = 3.35 x 10 8 Hz? ν = 3.35 x 10 8 Hz? λ = 2.57 x 10 2 m λ = 2.57 x 10 2 m

23. Photoelectric Effect Photoelectric effect –electrons are ejected from the surface of certain metals exposed to light of at least a certain minimum frequency Photoelectric effect –electrons are ejected from the surface of certain metals exposed to light of at least a certain minimum frequency irradiating a clean metal surface with light causes electrons to be ejected from the metal irradiating a clean metal surface with light causes electrons to be ejected from the metal Einstein – beam of light behaves as if it were compose of photons (stream of small particles) Einstein – beam of light behaves as if it were compose of photons (stream of small particles) Energy of photons: E = hν Energy of photons: E = hν Energy depends only on frequency of photon Energy depends only on frequency of photon Intensity of light beam – measure of number of photons, not energy Intensity of light beam – measure of number of photons, not energy

24. Photoelectric Effect Light energy can behave as both waves and small particles Light energy can behave as both waves and small particles Both matter and energy occur only in discrete units Both matter and energy occur only in discrete units Atoms – emit light quanta (photons) of a few specific energies Atoms – emit light quanta (photons) of a few specific energies Give rise to a line spectrum Give rise to a line spectrum

25. 5.5 – Wavelike Properties of Matter : The de Broglie Equation Einstein – relationship between mass and λ Einstein – relationship between mass and λ E = mc 2 or E = mc 2 or de Broglie – matter can behave in some respects like light de Broglie – matter can behave in some respects like light Both light and matter are wavelike as well as particlelike. Both light and matter are wavelike as well as particlelike. Relationship between λ of an electron or of any other particle or object of mass m moving at velocity v Relationship between λ of an electron or of any other particle or object of mass m moving at velocity v

26. Examples What is the de Broglie wavelength (in meters) of a pitched baseball with a mass of 120 g and speed of 100 mph (44.7 m/s) What is the de Broglie wavelength (in meters) of a pitched baseball with a mass of 120 g and speed of 100 mph (44.7 m/s) At what speed (in meter per second) must a 145 g baseball be traveling to have a de Broglie wavelength of 0.500 nm? At what speed (in meter per second) must a 145 g baseball be traveling to have a de Broglie wavelength of 0.500 nm?

27. 5.6 -Quantum Mechanics and the Heisenberg Uncertainty Principle A.Bohr – described the structure of the hydrogen atom as containing an electron circling the nucleus A.Bohr – described the structure of the hydrogen atom as containing an electron circling the nucleus 1.Specific orbits of the electrons correspond to specific energy levels 1.Specific orbits of the electrons correspond to specific energy levels 2.Quantum number: the smallest increment of energy 2.Quantum number: the smallest increment of energy i.Represented the energy difference of any two adjacent orbits i.Represented the energy difference of any two adjacent orbits

28. 5.6 -Quantum Mechanics and the Heisenberg Uncertainty Principle B.Schrödinger – quantum mechanical model of atom B.Schrödinger – quantum mechanical model of atom 1. Abandon idea of an electron as a small particle moving around the nucleus in a defined path 2.Concentrate on the electron's wavelike properties C.Heisenberg Uncertainty Principle – both the position (Δx) and the momentum (Δmv) of an electron cannot be known beyond a certain level of precision C.Heisenberg Uncertainty Principle – both the position (Δx) and the momentum (Δmv) of an electron cannot be known beyond a certain level of precision 1.(Δx) (Δmv) > h 4π 4π 2.Cannot know both the position and the momentum of an electron with a high degree of certainty

29. 5.6 -Quantum Mechanics and the Heisenberg Uncertainty Principle 3.If the momentum is known with a high degree of certainty i.Δmv is small ii.Δ x (position of the electron) is large 4.If the exact position of the electron is known i.Δmv is large ii.Δ x (position of the electron) is small

30. The Bohr Model of the Atom The Bohr Model of the Atom the Bohr model created by Niels Bohr depicts the atom as a small, positively charged nucleus surrounded by electrons that travel in circular orbits around the nucleus the Bohr model created by Niels Bohr depicts the atom as a small, positively charged nucleus surrounded by electrons that travel in circular orbits around the nucleus similar in structure to the solar system, but with electrostatic forces providing attraction, rather than gravity similar in structure to the solar system, but with electrostatic forces providing attraction, rather than gravity Describe the behavior of electrons in an atom Describe the behavior of electrons in an atom

31. 5.7 The Wave Mechanical Model of the Atom Schröndinger’s quantum mechanical model of atomic structure is frame in the form of a wave equation; describe the motion of ordinary waves in fluids. Schröndinger’s quantum mechanical model of atomic structure is frame in the form of a wave equation; describe the motion of ordinary waves in fluids. i. Wave functions or orbitals (Greek, psi , the mathematical tool that quantum mechanic uses to describe any physical system i. Wave functions or orbitals (Greek, psi , the mathematical tool that quantum mechanic uses to describe any physical system ii.  2 gives the probability of finding an electron within a given region in space ii.  2 gives the probability of finding an electron within a given region in space

32. 5.7 The Wave Mechanical Model of the Atom iii. Contains information about an electron’s position in 3-D space iii. Contains information about an electron’s position in 3-D space defines a volume of space around the nucleus where there is a high probability of finding an electron defines a volume of space around the nucleus where there is a high probability of finding an electron say nothing about the electron’s path or movement say nothing about the electron’s path or movement

33. 5.8 The Orbitals Orbital: the probability map for hydrogen electrons Orbital: the probability map for hydrogen electrons The principal quantum number (n): Shell The principal quantum number (n): Shell a. describes the size and energy level of the orbital a. describes the size and energy level of the orbital a. positive integer (n = 1, 2, 3 …..) a. positive integer (n = 1, 2, 3 …..) as the value of n increases as the value of n increases the number of allowed orbital increases the number of allowed orbital increases size of the orbital increases size of the orbital increases the energy of the electron in the orbital increases the energy of the electron in the orbital increases

34. The Orbitals As the value of n increases, the number of allowed orbitals increases and the size of the orbitals become larger, thus allowing an electron to be far from the nucleus, because it takes energy to separate a negative charge from a positive charge As the value of n increases, the number of allowed orbitals increases and the size of the orbitals become larger, thus allowing an electron to be far from the nucleus, because it takes energy to separate a negative charge from a positive charge E.gn = 3  third shell (period #3) E.gn = 3  third shell (period #3) n = 5  fifth shell (period # 5) n = 5  fifth shell (period # 5) n = 2  n = 2 

35. The orbitals The angular-momentum quantum number (l) The angular-momentum quantum number (l) defines the 3-D shape of orbital integral value from 0 to n-1 If n = 1, then l =0 If n = 1, then l =0 n = 2, then l = 0 or 1 n = 2, then l = 0 or 1 n = 3, then l = 0, 1 or 2 n = 3, then l = 0, 1 or 2 and so forth and so forth

36. The orbitals orbitals are grouping in group according to the angular-momentum quantum number l is called subshells. orbitals are grouping in group according to the angular-momentum quantum number l is called subshells. Quantum number l 01234 …. Quantum number l 01234 …. Subshell notation:spdfg Subshell notation:spdfg

37. The Orbitals.Describes the orbitals that are occupied by the electrons in an atom.Describes the orbitals that are occupied by the electrons in an atom B.Aufbau principle: in the ground state, the electrons occupy the lowest energy orbital first B.Aufbau principle: in the ground state, the electrons occupy the lowest energy orbital first Orbitals are grouping in group according to the angular-momentum quantum number l is called subshells. Orbitals are grouping in group according to the angular-momentum quantum number l is called subshells. Types of orbitals Types of orbitals Notations: s, p, d, f Notations: s, p, d, f

38. Subshell s S orbital S orbital Probability of finding an electron depends only on the distance of the electron from the nucleus Differences among s orbital in different shells Size increases in higher shells Electron distribution in outer s orbital has several different regions of maximum probability separated by a node Node – surface of zero probability Intrinsic property of a wave – zero amplitude at node

39. Subshell p dumbbell shape, are oriented on the 3-principle axes, x, y, and z dumbbell shape, are oriented on the 3-principle axes, x, y, and z Electron distribution concentrated in identical lobes on either side of the nucleus Electron distribution concentrated in identical lobes on either side of the nucleus Nodal plane cuts through nucleus Nodal plane cuts through nucleus probability of finding a p electron near the nucleus is zero probability of finding a p electron near the nucleus is zero

40. Subshell p have different phases have different phases crucial for bonding crucial for bonding Only lobes with same phase can interact to form covalent bonds Only lobes with same phase can interact to form covalent bonds Three p orbitals oriented along the x-, y-, and z-axes (px, py, pz) Three p orbitals oriented along the x-, y-, and z-axes (px, py, pz)

41. Subshell p

42. Subshell - d

43. examples Indicate whether each of the following statements about the atomic structure is true of false. Indicate whether each of the following statements about the atomic structure is true of false. An s orbital is always spherical in shape An s orbital is always spherical in shape The 2s orbital is the same size as the 3s orbital The 2s orbital is the same size as the 3s orbital The number of lobes on a p orbital increases as n increases. That is, a 3p orbital has mores lobes than a 2p orbital The number of lobes on a p orbital increases as n increases. That is, a 3p orbital has mores lobes than a 2p orbital Level 1 has one s orbital, level 2 has two s orbitals, level 3 has 3s orbitals and so on. Level 1 has one s orbital, level 2 has two s orbitals, level 3 has 3s orbitals and so on.

44. Summary Subslevels (type of orbitals) Present Subslevels (type of orbitals) Present 1s (1) 2s (1) 2p (3) 2s (1) 2p (3) 3s (1) 3p (3) 3d (5) 3s (1) 3p (3) 3d (5) 4s (1) 4p (3) 4d (5) 4f (7) 4s (1) 4p (3) 4d (5) 4f (7)

45. 5.10 The Wave Mechanical Model Pauli exclusion principle Pauli exclusion principle No two electrons in the same atom can have the same four quantum numbers (ms) No two electrons in the same atom can have the same four quantum numbers (ms) An orbital can hold at most two electrons An orbital can hold at most two electrons If two electrons are in the same orbital, they must have the opposite spin If two electrons are in the same orbital, they must have the opposite spin The spin quantum number (ms) refers to the two possible spin orientation of an electron: The spin quantum number (ms) refers to the two possible spin orientation of an electron: +1/2 (up-spin) or -1/2 (down-spin) +1/2 (up-spin) or -1/2 (down-spin)

46. 5.10 The Wave Mechanical Model E.Hund’s rule: if more than one orbital with the same energy level are available, one electron will occupy each orbital until all are filled, before putting a 2nd electron in any orbital (section 5.10) E.Hund’s rule: if more than one orbital with the same energy level are available, one electron will occupy each orbital until all are filled, before putting a 2nd electron in any orbital (section 5.10)

47. 5.12- Electron Arrangements in the First Eighteen Atoms on the Periodic Table Recall: Atomic number (Z) = # electrons = # protons Recall: Atomic number (Z) = # electrons = # protons Electron configuration: describes the orbitals that are occupied by the electrons in an atom Electron configuration: describes the orbitals that are occupied by the electrons in an atom Orbital diagrams: describe the orbitals with arrows representing electrons Orbital diagrams: describe the orbitals with arrows representing electrons a. Arrows are written up or down to denote electron’s spin a. Arrows are written up or down to denote electron’s spin

48. Example Write the full electron configuration and orbital filling diagram for: O, Na, Si, Cr Write the full electron configuration and orbital filling diagram for: O, Na, Si, Cr

49. Electrons Configuration Shorthand version – give the symbol of the noble gas in the previous row to indicate electrons in filled shells, and then specify only those electrons in unfilled shells Shorthand version – give the symbol of the noble gas in the previous row to indicate electrons in filled shells, and then specify only those electrons in unfilled shells E.g Shorthand version of P: [Ne] 3s 2 3p 3 E.g Shorthand version of P: [Ne] 3s 2 3p 3 The valence-shell electrons are the outer most shell of electron The valence-shell electrons are the outer most shell of electron E.gValence electrons of P is 5

50. 5.12 Electron Configurations and the Periodic Table Write the full electron configuration Write the full electron configuration short hand notation short hand notation Determine the valence electrons Determine the valence electrons Mg,Pd, Br Mg,Pd, Br

51. 5.15 Atomic Size A.Periodicity is the presence of regularly repeating pattern found in nature A.Periodicity is the presence of regularly repeating pattern found in nature B.Atomic radius is distance between the nuclei of two atoms bonded together B.Atomic radius is distance between the nuclei of two atoms bonded together C.Atomic radius increases down a group, decreases across a period C.Atomic radius increases down a group, decreases across a period i. Larger n, larger size of orbital i. Larger n, larger size of orbital

52. Examples In each of the following sets of elements, indicate which element has the smallest atomic size In each of the following sets of elements, indicate which element has the smallest atomic size Ba, Ca, Ra Ba, Ca, Ra P, Si, Al P, Si, Al Rb, Cs, K Rb, Cs, K

53. Ionization Energies Ionization energy (Ei) – the amount of energy required to remove the outermost electron from an isolated neutral atom in the gaseous state Ionization energy (Ei) – the amount of energy required to remove the outermost electron from an isolated neutral atom in the gaseous state

54. Examples Which has higher ionization energy (Ei)? Which has higher ionization energy (Ei)? K or Br K or Br S or Te S or Te Ne or Sr Ne or Sr