1. Electronic Structure of Atoms
Unit H
Electronic Structure of Atoms

2. Electromagnetic radiation
All types of EMR move through a vacuum at the speed of light (~3 x 108 m/s) but have distinct
Wavelength (λ) – distance between peaks
Energy (E)
Frequency (ν) = # of times a wave passes a certain point
Much of our understanding of the electronic structure of atoms has come from analysis of light either emitted or absorbed by substances

3. Quantitatively describing light
λν = c (speed of light)
Inverse relationship between frequency & wavelength
E = hν
Max Planck – energy can only be released or absorbed by atoms is discrete “chunks” – quantum (smallest quantity of energy)
h = Planck’s constant x J-s
Matter can emit/absorb energy in whole number multiples of hv

4. Which light has the least amount of energy?
Infrared
Microwaves
Green light
Gamma
Ultraviolet

5. Which light has the least amount of energy?
Infrared
Microwaves
Green light
Gamma
Ultraviolet

6. Which light has the highest frequency?
Red
Orange
Yellow
Green
Blue

7. Which light has the highest frequency?
Red
Orange
Yellow
Green
Blue

8. Line Spectra
A spectrum containing radiation of only certain wavelengths = a line spectrum

9. Energy levels in the H atom from the bohr model
If the transition of an electron from the n = 3 state to the n = 2 state results in emission of visible light, is the transition from the n = 2 state to the n = 1 state more likely to result in the emission of infrared or ultraviolet radiation?

10. Energy levels in the H atom from the bohr model
A transition from n = 2 to n = 1 involves a greater energy change than n = 3 to n = 2. UV has greater energy/smaller wavelength than Infrared.

11. Three postulates of Bohr’s model
Only orbits of certain radii, corresponding to certain specific energies, are permitted for the electron in a hydrogen atom.
An electron in a permitted orbit is in an “allowed” energy state. An electron in an allowed energy state does not radiate energy, and therefore, does not spiral into the nucleus.
Energy is emitted or absorbed by the electron only as the electron changes from one allowed energy state to another. This energy is emitted or absorbed as a photon that has energy E = hν

13. In a hydrogen atom, an electron undergoing the transition between which energy levels would emit the most energy?
3 – 2
5 – 2
1 – 4
4 – 5
4 – 1
2 – 1

14. In a hydrogen atom, an electron undergoing the transition between which energy levels would emit the most energy?
3 – 2
5 – 2
1 – 4
4 – 5
4 – 1
2 – 1
Energy is emitted only for transitions from higher to lower energy levels.
Transitions to the 1st energy level are always more energy than to other energy levels.

15. In a hydrogen atom, an electron undergoing which transition between energy levels would emit red light?
3 – 2
5 – 2
1 – 2
4 – 5
4 – 1
2 – 1

16. In a hydrogen atom, an electron undergoing which transition between energy levels would emit red light?
3 – 2
5 – 2
1 – 2
4 – 5
4 – 1
2 – 1
Energy is emitted when electrons drop back to their ground state. The 3-2 transition is lower energy than the 4-2 (teal) or 5-2 (violet).
All transitions to the 1st energy level are too high energy and so would be in the ultraviolet range.

17. Which graph best represents the relationship between wavelength and frequency for EMR?

18. Which graph best represents the relationship between wavelength and frequency for EMR?
Wavelength (λ) and frequency (ν) are inversely related.

19. Quantum mechanical model
Bohr’s model introduced a single quantum number, n, to describe an orbit.
The quantum mechanical model uses three quantum numbers, n, l, and ml, which result naturally from the mathematics used to describe an orbital.

20. Quantum Mechanical model
The principle quantum number, n, can have positive integral values 1, 2, 3….
As n increases, the orbital becomes larger, and e- spends more time farther from nucleus.
An increase in n also means that the e- has a higher energy and is therefore less tightly bound to the nucleus.

21. Quantum Mechanical model
The 2nd quantum number = the angular momentum quantum number, l, can have integral values from 0 to (n-1) for each value of n.
This quantum number defines the shape of the orbital.
The value of l for a particular orbital is generally designated by the letters: s, p, d, and f, corresponding to l values of 0, 1, 2, and 3:
Come from the words sharp, principal, diffuse, and fundamental (used to describe features of spectra before quantum mechanics was developed.)
Value of l 1 2 3
Letter used s p d f

22. Quantum mechanical model
The magnetic quantum number, ml , can have integral values between -1 and 1, including 0.
This quantum number describes the orientation of the orbital in space

23. shape of the s orbital

24. Shape of the p orbital

25. Shape of D orbitals

26. Shape of F Orbitals

27. Shape of Orbitals

28. NS 4 Electron Configurations

29. General energy ordering for a many-electron atom

30. General energy ordering for a many-electron atom

33. condensed electron configurations
Write the electron configuration for Na
1s22s22p63s1
Write the electron configuration for Ne
1s22s22p6
We can write a condensed electron configuration for sodium as
[Ne]3s1
A condensed electron configuration includes writing nearest noble gas element of lower atomic number in brackets and then adding the correct number of electrons afterwards.

34. Condensed electron configurations
The electrons that are represented by the bracketed symbol are referred to noble-gas core. Core electrons = inner shell electrons
The electrons after the noble gas core are called outer-shell electrons, also known as valence electrons. (Involved in bonding)

36. Write the entire electron configuration for 35Br.
Then turn this into a condensed electron configuration.

37. Write the entire electron configuration for 35Br.
Then turn this into a condensed electron configuration.
1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p5

38. Write the entire electron configuration for 35Br.
Then turn this into a condensed electron configuration.
1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p5
[Ar] 4s2 3d10 4p5

39. Write the condensed electron configuration for 33As Sketch an orbital notation for this.

40. Write the condensed electron configuration for 33As Sketch an orbital notation for this. [Ar] 4s2 3d10 4p3 [Ar] ___ ___ ___ ___ ___ ___ ___ ___ ___

41. Write the electron configuration for the single highest energy subset (sublevel) that describes 50Sn in its ground state.

42. Write the electron configuration for the single highest energy subset (sublevel) that describes 50Sn in its ground state. 5p2

43. Write the condensed electron configuration that describes the 35Br atom and then the 35Br- ion in their ground state.

44. Write the condensed electron configuration that describes the 35Br atom and then the 35Br- ion in their ground state. Br atom: [Ar] 4s2 3d10 4p5 Br- ion: [Ar] 4s2 3d10 4p6

45. Write the entire electron configuration for the 12Mg atom and the 12Mg2+ ion in its ground state.

46. Write the entire electron configuration for the 12Mg atom and the 12Mg2+ ion in its ground state. Mg atom: 1s2 2s2 2p6 3s2 Mg2+ ion: 1s2 2s2 2p6

47. What atom does this electron configuration represent? 1s2 2s2 2p6 3p3

48. What atom does this electron configuration represent
What atom does this electron configuration represent? Look carefully, maybe this helps. 1s2 2s2 2p6 3p3 1s2 2s2 2p6 3s0 3p3

49. What atom does this electron configuration represent
What atom does this electron configuration represent? Look carefully, maybe this helps. 1s2 2s2 2p6 3p3 1s2 2s2 2p6 3s0 3p3 Al in an excited state. The 3s2 electrons have been promoted to the p sublevel.

50. Write the condensed electron configuration that describes 28Ni atom, and then 28Ni2+ ion in its ground state.

51. Write the condensed electron configuration that describes 28Ni atom, and then 28Ni2+ ion in its ground state. Ni: [Ar] 4s2 3d8 Ni2+: [Ar] 3d8 NOT [Ar] 4s2 3d6
Transition metals will lose the s orbital electrons from the higher quantum number before they lose the d orbital electrons when they become ions.

52. Name the element that is described by an atom electron configuration of the highest energy orbital of the element in its ground state: 4d4

53. Name the element that is described by an atom electron configuration of the highest energy orbital of the element in its ground state: 4d4 42Mo

54. Name three (common) naturally occurring particles (atoms or ions) that are isoelectronic with Cl-

55. Name three (common) naturally occurring particles (atoms or ions) that are isoelectronic with Cl- Same number of electrons (18) Ar, S2-, K+, Ca2+, V5+

56. What is the electron configuration of the valence electrons of selenium?
4s2 4p4
4p4
4s2 3d10 4p4
4d4
4s2 4d10 4p4

57. What is the electron configuration of the valence electrons of selenium?
4s2 4p4
4p4
4s2 3d10 4p4
4d4
4s2 4d10 4p4
Some books consider the d electrons to be valence electrons, but most do NOT. AP will refer only to s and p as valence electrons.

58. How many unpaired electrons does selenium have?

59. How many unpaired electrons does selenium have
How many unpaired electrons does selenium have? [Ar] 4s2 4p4 ___ ___ ___ ___