1. Chapter 2 Atoms, Molecules, and Ions
Chemistry, The Central Science, 12th edition
Theodore L. Brown; H. Eugene LeMay, Jr.; and Bruce E. Bursten
Chapter 2 Atoms, Molecules, and Ions kr

2. Roadmap chapter 2:
Basic material building blocks/things (electrons, neutrons, protons ) and electromagnetic radiation
Basic material structures: atoms, ions, isotops, molecules , etc.

3. The Electron
Figure 2.4
Streams of negatively charged particles were found to emanate from cathode tubes.
J. J. Thompson is credited with their discovery (1897).

4. Discovery of the Nucleus
Ernest Rutherford shot  particles at a thin sheet of gold foil and observed the pattern of scatter of the particles.
Figure 2.10

5. The Modern Atom
Rutherford postulated a very small, dense nucleus with the electrons around the outside of the atom.
Most of the volume of the atom is empty space.
Figure 2.12
1 Angstrom = 0.1nm
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6. Other Subatomic Particles
Protons were discovered by Rutherford in 1919.
Neutrons were discovered by James Chadwick in 1932.
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7. Part 4

8. Subatomic Particles
Protons and electrons are the only particles that have a charge.
Protons and neutrons have essentially the same mass.
The mass of an electron is so small we ignore it.
Table 2.1
1 amu = g
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9. Atoms and elements
Atoms of different elements have different number of protons
All atoms of an element have the same number of protons, but different numbers of electrons (ions) or neutrons (isotopes).

10. Symbols of Elements Elements are symbolized by one or two letters.
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11. Atomic Number
All atoms of the same element have the same number of protons:
The atomic number (Z)
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12. Atomic Mass
The mass of an atom in atomic mass units (amu) is the total number of protons and neutrons in the atom.
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13. Isotopes
Isotopes are atoms of the same element with different masses.
Isotopes have different numbers of neutrons. 11 6 C 12 6 C 13 6 C 14 6 C
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14. Neutrals vs. Ions Ions: positive are ca+ions
Cation is missing electron(s)
p>e
Ne +
Ions: negative are anions
Anion has extra electrons
p<e
O2-

15. Atomic Mass
Atomic and molecular masses can be measured with great accuracy with a mass spectrometer.
Figure 2.13
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16. Mass Number is Not the Same as Atomic Mass
the atomic mass is an experimental number determined from all naturally occurring isotopes
the mass number refers to the number of protons + neutrons in one isotope
natural or man-made
Part 4

17. FYI: Calculating Atomic Mass
Gallium has two naturally occurring isotopes: Ga-69 with mass amu and a natural abundance of 60.11% and Ga-71 with mass amu and a natural abundance of 39.89%. Calculate the atomic mass of gallium.
Solution:
Convert the percent natural abundance into decimal form.
Ga-69 
Ga-71 
Determine the Formula to Use
Atomic Mass = (abundance1)∙(mass1) + (abundance2)∙(mass2) + ...
Apply the Formula:
Atomic Mass = ( amu) ( amu)
= amu
Part 4

18. Average Mass
Because in the real world we use large amounts of atoms and molecules, we use average masses in calculations.
Average mass is calculated from the isotopes of an element weighted by their relative abundances.
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19. Periodic Table as databank Have your own PT !!!
It is a systematic catalog of the elements.
Elements are arranged in order of atomic number.
Find what data are in your PT for each element!!!!
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20. PT Find what data are in your PT for each element!!!!
What is the unit of the average mass?
What is mole?

21. Periodicity
When one looks at the chemical properties of elements, one notices a repeating pattern of reactivities.
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22. Periodic Table The rows on the periodic chart are periods.
Columns are groups.
Elements in the same group have similar chemical properties.
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23. Groups These five groups are known by their names.
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24. Periodic Table
Nonmetals are on the right side of the periodic table (with the exception of H).
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25. Periodic Table
Metalloids border the stair-step line (with the exception of Al, Po, and At).
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26. Periodic Table Metals are on the left side of the chart.
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27. Elements, Molecules, Compounds
What is a molecule?
What is N2?
What is a compound?
What is a molecular compound?
What is ionic compound?

28. Chemical Formulas
The subscript to the right of the symbol of an element tells the number of atoms of that element in one molecule of the compound.
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29. Chemical Formulas
Molecular compounds are composed of molecules and almost always contain only nonmetals.
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30. Diatomic Molecules
These seven elements occur naturally as molecules containing two atoms.
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31. Types of Formulas
Empirical formulas give the lowest whole-number ratio of atoms of each element in a compound.
Molecular formulas give the exact number of atoms of each element in a compound.
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32. Types of Formulas
Structural formulas show the order in which atoms are bonded.
Perspective drawings also show the three-dimensional array of atoms in a compound.
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33. Ions –common charges
When atoms lose or gain electrons, they become ions.
Cations are positive and are formed by elements on the left side of the periodic chart.
Anions are negative and are formed by elements on the right side of the periodic chart.
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34. Ionic Bonds
Ionic compounds (such as NaCl) are generally formed between metals and nonmetals.
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35. Writing Formulas
Because compounds are electrically neutral, one can determine the formula of a compound this way:
The charge on the cation becomes the subscript on the anion.
The charge on the anion becomes the subscript on the cation.
If these subscripts are not in the lowest whole-number ratio, divide them by the greatest common factor.
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36. Common Cations
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37. Common Anions
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38. Inorganic Nomenclature
Write the name of the cation.
If the anion is an element, change its ending to -ide; if the anion is a polyatomic ion, simply write the name of the polyatomic ion.
If the cation can have more than one possible charge, write the charge as a Roman numeral in parentheses.
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39. Patterns in Oxyanion Nomenclature
When there are two oxyanions involving the same element:
The one with fewer oxygens ends in -ite.
NO2− : nitrite; SO32− : sulfite
The one with more oxygens ends in -ate.
NO3− : nitrate; SO42− : sulfate
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40. Patterns in Oxyanion Nomenclature
The one with the second fewest oxygens ends in -ite.
ClO2− : chlorite
The one with the second most oxygens ends in -ate.
ClO3− : chlorate
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41. Patterns in Oxyanion Nomenclature
The one with the fewest oxygens has the prefix hypo- and ends in -ite.
ClO− : hypochlorite
The one with the most oxygens has the prefix per- and ends in -ate.
ClO4− : perchlorate
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42. Acid Nomenclature
If the anion in the acid ends in -ide, change the ending to -ic acid and add the prefix hydro- .
HCl: hydrochloric acid
HBr: hydrobromic acid
HI: hydroiodic acid
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43. Acid Nomenclature
If the anion in the acid ends in -ite, change the ending to -ous acid.
HClO: hypochlorous acid
HClO2: chlorous acid
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44. Acid Nomenclature
If the anion in the acid ends in -ate, change the ending to -ic acid.
HClO3: chloric acid
HClO4: perchloric acid
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45. Nomenclature of Binary Compounds
The less electronegative atom is usually listed first.
A prefix is used to denote the number of atoms of each element in the compound (mono- is not used on the first element listed, however) .
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46. Nomenclature of Binary Compounds
The ending on the more electronegative element is changed to -ide.
CO2: carbon dioxide
CCl4: carbon tetrachloride
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47. Nomenclature of Binary Compounds
If the prefix ends with a or o and the name of the element begins with a vowel, the two successive vowels are often elided into one.
N2O5: dinitrogen pentoxide
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48. Nomenclature of Organic Compounds
Organic chemistry is the study of carbon.
Organic chemistry has its own system of nomenclature.
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49. Nomenclature of Organic Compounds
The simplest hydrocarbons (compounds containing only carbon and hydrogen) are alkanes.
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50. Nomenclature of Organic Compounds
The first part of the names above correspond to the number of carbons (meth- = 1, eth- = 2, prop- = 3, etc.).
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51. Nomenclature of Organic Compounds
When a hydrogen in an alkane is replaced with something else (a functional group, like -OH in the compounds above), the name is derived from the name of the alkane.
The ending denotes the type of compound.
An alcohol ends in -ol.
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52. Example : Determining the Number of Protons and Electrons in an Ion

53. Find the number of protons and electrons in the Ca2+ ion.
Example:
Find the number of protons and electrons in the Ca2+ ion.
Part 4

54. Example: Find the number of protons and electrons in the Ca2+ ion
Write down the given quantity and its units.
Given: Ca2+
Part 4

55. Example: Find the number of protons and electrons in the Ca2+ ion
Information
Given: Ca2+
Write down the quantity to find and/or its units.
Find: #p and #e
Part 4

56. Example: Find the number of protons and electrons in the Ca2+ ion
Information
Given: Ca2+
Find: #p and #e
Design a Solution Map.
ion symbol
#p and #e #p #e
element
atomic number
Part 4

57. Example: Find the number of protons and electrons in the Ca2+ ion
Information
Given: Ca2+
Find: #p and #e
Solution Map: ion symbol  element  atomic number  #p  #e
Apply the Solution Map.
Determine the Name of the Element
Ca = calcium
Part 4

58. Example: Find the number of protons and electrons in the Ca2+ ion
Information
Given: Ca2+ = calcium
Find: #p and #e
Solution Map: ion symbol  element  atomic number  #p  #e
Apply the Solution Map.
Determine the Atomic Number of the Element
Ca = calcium
Atomic Number = 20
Part 4

59. Example: Find the number of protons and electrons in the Ca2+ ion
Information
Given: Ca2+ = calcium, Z = 20
Find: #p and #e
Solution Map: ion symbol  element  atomic number  #p  #e
Apply the Solution Map.
Determine the Number of Protons in an Atom of the Element
Ca = calcium
Atomic Number = 20
#p = atomic number = 20
Part 4

60. Example: Find the number of protons and electrons in the Ca2+ ion
Information
Given: Ca2+ = calcium, Z = 20
Find: #p = 20 and #e
Solution Map: ion symbol  element  atomic number  #p  #e
Apply the Solution Map.
Determine the Number of Electrons in an Ion of the Element
Ca = calcium
Atomic Number = 20
#p = atomic number = 20
Ion Charge = #p - #e
+2 = 20 - #e
-18 = - #e
18 = #e
Part 4

61. Atomic Structures of Ions
Part 4

62. Atomic Structures of Ions
Part 4

63. Ion Charge & the Periodic Table
the charge on an ion can often be determined from an elements position on the Periodic Table
metals are always positive ions, nonmetals are negative ions
for many main group metals, the charge = the group number
for nonmetals, the charge = the group number - 8
Part 4

64. IA VIA IIA IIIA VA VIIA Li+1 Be+2 N-3 O-2 F-1 Na+1 Mg+2 Al+3 P-3 S-2
Cl-1
K+1
Ca+2
Ga+3
As-3
Se-2
Br-1
Rb+1
Sr+2
In+3
Te-2
I-1
Cs+1
Ba+2
Part 4

65. Structure of the Nucleus
Soddy discovered that the same element could have atoms with different masses, which he called isotopes
there are 2 isotopes of chlorine found in nature, one that has a mass of about 35 amu and another that weighs about 37 amu
The observed mass is a weighted average of the weights of all the naturally occurring atoms
the atomic mass of chlorine is amu
Part 4

66. Isotopes all isotopes of an element are chemically identical
undergo the exact same chemical reactions
all isotopes of an element have the same number of protons
isotopes of an element have different masses
isotopes of an element have different numbers of neutrons
isotopes are identified by their mass numbers
protons + neutrons
Part 4

67. Isotopes Atomic Number Number of protons Z Mass Number
Protons + Neutrons
Whole number A
Abundance = relative amount found in a sample
Part 4

68. Neon 9.25% 22 12 10 Ne-22 or 0.27% 21 11 Ne-21 or 90.48% 20 Ne-20 or
Percent Natural Abundance
A, Mass Number
Number of Neutrons
Number of Protons
Symbol
Part 4

69. Isotopes
Cl-35 makes up about 75% of chlorine atoms in nature, and Cl-37 makes up the remaining 25%
the average atomic mass of Cl is amu
Cl-35 has a mass number = 35, 17 protons and 18 neutrons ( ) Cl 35 17
Atomic Symbol
A = mass number
Z = atomic number AX Z
= X-A
Part 4

70. Example: Determining the Number of Protons and Neutrons from Isotope Symbols

71. How many protons and neutrons in the chromium isotope
Example:
How many protons and neutrons in the chromium isotope
Part 4

72. Example: How many protons and neutrons in the chromium isotope
Write down the given quantity and its units.
Given:
Part 4

73. Example: How many protons and neutrons in the chromium isotope
Information
Given:
Write down the quantity to find and/or its units.
Find: #p and #n
Part 4

74. Example: How many protons and neutrons in the chromium isotope
Information
Given:
Find: #p and #n
Design a Solution Map.
ion symbol
#p and #n #p #n
element
atomic number
Part 4

75. Example: How many protons and neutrons in the chromium isotope
Information
Given:
Find: #p and #n
Solution Map: ion symbol  element  atomic number  #p  #n
Apply the Solution Map.
Determine the Name of the Element
Cr = chromium
Part 4

76. Example: How many protons and neutrons in the chromium isotope
Information
Given: = calcium
Find: #p and #n
Solution Map: ion symbol  element  atomic number  #p  #n
Apply the Solution Map.
Determine the Atomic Number of the Element
Cr = chromium
Atomic Number = 24
Part 4

77. Example: How many protons and neutrons in the chromium isotope
Information
Given: = calcium
Find: #p and #n
Solution Map: ion symbol  element  atomic number  #p  #n
Apply the Solution Map.
Determine the Number of Protons in an Atom of the Element
Cr = chromium
Atomic Number = 24
#p = atomic number = 24
Part 4

78. Example: How many protons and neutrons in the chromium isotope
Information
Given: = calcium
Find: #p and #n
Solution Map: ion symbol  element  atomic number  #p  #n
Apply the Solution Map.
Determine the Number of Neutrons in an Atom of the Element
Cr = chromium
Atomic Number = 24
#p = atomic number = 24
Mass Number = #p + #n
52 = 24 + #n
28 = #n
Part 4

79. Practice - Complete the following table
Part 4

80. Practice - Complete the following table
Part 4