1. Chapter 10
Modern Atomic Theory
and the Periodic Table
The amazing
colors in these
fireworks
explosions are
the result of
electrons
transferring
between energy
Introduction to General, Organic, and Biochemistry 10e
levels in atoms. John Wiley & Sons, Inc
Morris Hein, Scott Pattison, and Susan Arena

2. Chapter Outline
10.1 A Brief History 10.5 Atomic Structures of the
10.2 Electromagnetic Radiation First 18 Elements
10.3 The Bohr Atom 10.6 Electron Structures and
the Periodic Table
10.4 Energy Levels of
Electrons
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3. Electromagnetic Radiation
Frequency tells how many waves pass a particular
point per second.
Speed tells how fast a wave moves through space.
Figure 10.1 The wavelength of this wave is shown by
λ. It can be measured from peak to peak or trough to
trough.
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4. The Electromagnetic Spectrum
Visible light is only a small part of the electromagnetic
spectrum.
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5. Your Turn!
The number of waves that pass a particular point per
second is known as
a. Frequency
b. Wavelength
c. Amplitude
d. Speed
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6. Your Turn!
The color of visible light is determined by its
a. Speed
b. Wavelength
c. Amplitude
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7. Bohr Model (1912-1913)
Danish physicist Niels Bohr
proposed that electrons in
an atom are organized
into discrete energy
levels.
He pictured the negative
electrons in orbits around
the positive nucleus.
His evidence: the line
spectra of the elements.
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8. Line Spectrum
Atoms absorb energy to give off light..
Prisms or diffraction gratings separate the light into a
line spectrum for the element.
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9. Line Spectrum
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10. *Why so many lines?
Absorbed
5 energy
4
3
Released
2 energy
Each line in the spectrum
corresponds to electrons
moving from a higher energy
1 level to a lower energy level.
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11. Your Turn!
Review Question #5: What is meant when we say the
electron structure of an atom is in its ground state?
a. The highest possible energy level for an electron
b. The lowest possible energy level for an electron
c. Excited state
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12. Bohr Model
Was based on electrons having fixed energy levels and
therefore quantized amounts of energy.
Accounted for spectral lines.
Worked very well for hydrogen but did not work well
for heavier atoms.
Another model is needed that describes the behavior of
electrons as waves.
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13. The Wave-Mechanical Model
This mathematical model of the
atom describes the energy of
the electron with some
certainty, but the actual
location of the electron is
uncertain.
An orbital is …
the region in space where there is
a high probability of finding an
Review Questionwith a given energy.
electron 1
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14. Energy Levels of Electrons
Electrons in atoms are organized
into discrete principal energy
levels (n, where n is an integer).
Lowest energy level is n = 1, then
n = 2, etc.
As n increases, the energy of the
electron increases, and the
electron is on average further
from the nucleus.
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15. Sublevels
Energy levels are subdivided into
sublevels. Each sublevel has
orbitals.
Review Question 7: What letters are used to designate
the Orbital are designated by
types of orbitals?
s, p, d and f.
n = 1 has the sublevel 1s.
n = 2 has the sublevels 2s and 2p.
Each sublevel is made up of orbitals
of the same type and energy. 10-15

16. Electron Spin
Review Question 2: What conditions allow a 2nd electron to enter an orbital
Each electron in an atom appears to be spinning on its
axis.
Pauli exclusion principle states that an atomic orbital
can hold a maximum of two electrons, which must
have opposite spin.
What is the maximum number of electrons in any
orbital?
2
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17. s Sublevels
Review Question 6: How do 1s and 2s differ?
Every principal energy level has an s
sublevel that contains a single s
orbital which is farther away. (1s,
2s, 3s, etc.)
There is a 90% probability of finding
the electron within a spherical
region surrounding the nucleus.
Review Question 6: How are 1s and 2s alike?
Each s orbital is the same shape and
holds 2 electrons with opposite
spin.
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18. p Sublevels
Every principal energy level starting at n = 2 has a p
sublevel (2p, 3p, etc.) that contains 3 equal energy p
orbitals. The orbitals only differ by their orientation in
3-D space.
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19. Your Turn!
What is the maximum number of electrons in a 2p
orbital?
a. 2 A 2p sublevel holds 6 electrons, 2
b. 4 electrons per orbital.
c. 6
The maximum number of electrons in
d. 8 ANY orbital is 2.
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20. d Sublevels
Every principal energy level starting at n = 3 has a d
sublevel (3d, 4d, etc.) that contains 5 equal energy d
orbitals. These orbitals have more complex shapes
and are higher in energy than the s and p orbitals.
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21. Your Turn!
What is the maximum number of electrons in a 3d
sublevel?
a. 2 A 3d sublevel has 5 orbitals, so it holds
b. 4 10 electrons, 2 electrons per orbital.
c. 6
d. 10
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22. Summary
Each subshell is composed of orbitals
The number of orbitals depends on the subshell
2 electrons per orbital
Sublevel s p d f
Number of Orbitals 1 3 5 7
Electrons 2 6 10 14
Review Question 9
Shape sphere fig. 8 lobes hard to visualize
Review Question 10: Difference between orbital & Sons, Inc orbit?
Copyright 2012 John Wiley
and Bohr 10-22

23. Rules for Distributing Electrons
1. No more than two electrons can occupy one orbital.
2. Electrons occupy the lowest energy orbitals
available. s < p < d < f for a given value of n
3. Each orbital in a sublevel is occupied by a single
electron before a second electron enters. (Hunds
Rule)
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24. Your Turn!
In the fourth principal energy level, which sublevel
contains electrons with the greatest
energy?
a. 4s
b. 4p
c. 4d
d. 4f
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25. Your Turn!
How many orbitals are found in a 5p sublevel?
a. 1 The number of orbitals found in ANY
b. 3 energy level is 3.
c. 5
d. 7
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26. Your Turn!
What is the maximum number of electrons that can
occupy the third principal energy level?
a. 2
3s = 2
b. 6 3p = 6
c. 8 3d = 10
d. 18 2+6+10 = 18
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27. Atomic Structure
One way to indicate atomic structure shows the
structure of the nucleus and the number of electrons
in each energy level.
Review Question 8: List in order of increasing energy?
2s 2p 4s 1s 3d 4p 3s
1s 2s 2p 3s 3p 3d 4s 4p
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28. Electron Configuration
Another useful atomic structure shows the distribution
of electrons in the atom.
4 is the energy level, f is the orbital in the sublevel and 3
is the number of electrons
Review Question 13: An element has the designation 4f 3.
What is the significance of the 2012 f & 3?& Sons, Inc
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29. Orbital Diagram
Electron configurations can also be shown with orbital
diagrams. Each box represents an orbital.
Up and down arrows represent electrons of opposite
spin.
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30. Atomic Structure
orbital
3Li 1s22s1 4Be 1s22s2
1s 2s 1s 2s
5B 1s22s22p1
1s 2s 2p
sublevel
6C 1s22s22p2
1s 2s 2p
7N 1s22s22p2
1s 2s 2p
8O 1s22s22p2
1s 2s 2p
Energy
level Copyright 2012 John Wiley & Sons, Inc 10-30

31. Atomic Structure
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32. Atomic Structure
Remember to sum the superscripts in the electron configuration.
They should add up to the atomic number for the element.
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33. Valence Electrons
The valence electrons …
include all of the electrons in the highest principal
quantum number (the outermost energy level).
These electrons are the electrons that are involved in
bonding.
Review Question 4
Phosphorus: 1s2 2s2 2p6 3s2 3p3
Phosphorus has 5 valence electrons.
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34. Your Turn!
Atoms of which element have the following electron
configuration?
1s2 2s2 2p6 3s23p6
a. Cl
b. Ca
c. Ar
d. S
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35. The Periodic Table
Each horizontal row in the periodic table is called a
period.
The number of each period corresponds to the
outermost energy level of the element.
For example, Ar is in period 3 and its outermost energy
level is 3.
1s2 2s2 2p6 3s23p6
Argon has 8 electrons in energy level 3. Eight is the
most of any period.
Review Question 18: What is Copyright 2012 Johnnumber ofInc
the greatest Wiley & Sons, electrons in a period? 10-35

36. The Periodic Table
Groups or Families (a column) contain elements
whose properties are similar.
Representative Elements – A Groups
• Alkali Metals –1A
• Alkaline Earth Metals – 2A
• Halogens – 7A
• Noble Gases – 8A
O, S &Se
Review Question 17: Write the symbols of the first 3 elements with 6 electrons in their
Copyright 2012 John Wiley & Sons, Inc 10-36
outermost energy level?

37. Other Groups to Know
Transition Metals – B Groups
Inner Transition Metals
– Lanthanides (Rare Earth) – Atomic Nos. 58 -71
– Actinides – Atomic Nos. 90 – 103
Last electron in Group A goes into p sublevel.
Last electron in Group B goes into d sublevel.
Review Question 19: How does the placement of the last electron in Group A differ
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from Group B elements?

38. Your Turn!
Which element is a transition element?
a. sodium
b. fluorine
c. copper
d. lead
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39. Your Turn!
Chlorine is a member of what family of elements?
a. Noble gases
b. Alkali metals
c. Halogens
d. Chalcogens
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40. Valence Electrons and Groups
In the following groups, the group number is the number
of valence electrons.
Elements within a group have the same valence electron
configuration.
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41. Your Turn!
In which category of the periodic table does each
element contain valence electrons in the
second principal energy level?
a. The alkaline earth elements
b. The alkali metals
c. Group 2A
d. Period 2
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42. Your Turn!
On the periodic table, elements in the same group
contain the same number of
a. Protons
b. Electrons
c. Principal energy levels in their ground state
d. Valence electrons in their ground state
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43. Electron Configurations
and the Periodic Table
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44. Electron Configurations
and the Periodic Table
1. The number of the period corresponds with the
highest occupied energy level.
2. The group numbers for the representative elements
are equal to the total number of valence electrons.
3. The elements within a group have the same number of
valence electrons.
4. The elements within each of the s, p, d, f blocks are
filling s, p, d, f orbitals.
5. There are discrepancies within the transition elements.
Review Question 20: Where on the periodic table are elements not in the proper sequence
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according to atomic mass.

45. Abbreviated Electron Configurations
Use the symbol of the nearest preceding noble gas to
represent the electron configuration of the core
electrons.
Phosphorus: 1s2 2s2 2p6 3s2 3p3
Core Valence
Electrons [Ne] 3s2 3p3 Electrons
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46. Your Turn!
The electron configuration, [Ar] 4s1, is the ground state
electron configuration of
a. Potassium
b. Phosphorous
c. Fluorine
d. Sodium
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47. Your Turn!
The electron configuration, [Ne] 3s2 3p1, is the ground
state electron configuration of
a. Sodium
b. Aluminum
c. Argon
d. Sulfur
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48. Questions
Review Questions
– Did in class
Paired Questions (pg 210)
– Do 1, 5, 9, 13, 17, 21, 25, 29, 33, 37, 41, 45, 49
– Practice later every other even (2, 6, etc)
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