Chapter One

1
Subatomic Particles
---in a neutral atom e- p

• Define All atoms of a given element have the
  same protons
• This is the Atomic Number (Z)

13
Al
26.981
2
Mass Number (A)

• A ? protons ? neutrons
• estimation of atomic mass
• an atom of a particular composition symbolized
  by

mass element symbol atomic
3
Isotopes

• a single element (w/ fixed protons) can have
  various s of neutrons.
• variations called ISOTOPES.

1 1 2 1 3 1
hydrogen 1p 0n 1e-
H deuterium 1p 1n 1e-
H tritium 1p 2n 1e- H does
not occur in nature
4
17
Atomic Masses on Periodic Table
Cl
35.453
weighted average of all the isotopes of an
element
? (atomic mass x natural abundance) of each
isotope
e.g. 2 isotopes of Cl are 35Cl (34.97 amu,
75.50) 37Cl (36.97 amu, 24.50). What
is the observed atomic mass of Cl?
75.50 24.50 100
100
-------- (34.97 amu) ------- (36.97 amu)
35.45 amu
note if exact mass of isotope is not
given, approximate as being A
5
Weighted Average Quiz Grades
Say that a student receives the following quiz
grades 8, 9, 8, 8, 10, 10, 9, 8, 8, 9 so 50
are 8s 30 are 9s 20 are 10s
weighted average
5 3 2 10
10 10
---- (8) ---- (9) ---- (10) 8.7
no individual quiz has this score
6
How far to the nearest star?
7
Quantitative Relationships in Chemistry

• Two ways of quantifying matter
• based on weight (mass) easy, but not always
  useful
• based on entities (number) useful, but not
  always easy
• 2H2 O2 -----gt 2H2O

8
The Mole

• 6.022 x 1023 of anything (atoms, cars, etc)
• 1 MOLE
• N Avogadros Number
• Use as conversion factor
• 1 mole Fe 6.022 x 1023 atoms Fe
• 0.5162 mole Fe x 6.022 x 1023 atoms /mole
• 3.109 x 1023 atoms Fe
• 1.4 x 1024 atoms Fe x (1 mole/6.022 x 1023 atoms)
  
• 2.3 mole Fe

9
Molar Mass

• Define Molar Mass
• mass in grams of 1 mole of the atom
• ---numerically equal to the mass of the basic
  unit in amu
• e.g. 12C 1 atom 12 amu
• 1 mole 12C 12 g
• Have, therefore, related mass (which we can
  measure) and number (which we can use).
• Can convert between one and another as needed.
• 24.305g Mg 1 mole Mg 6.022 x 1023 atoms Mg

10
Relationship Between Mole and Mass
1 mole 6.022 x 1023 atoms
11
Molecular Masses

• ? atomic masses of atoms in molecule
• e.g. H2O 2(1.01 g/mole) 1(16.00 g/mole)
• 18.02 g/mole
• e.g. H2SO4 2(1.01 g/mole) 1(32.07 g/mole)
  4(16.00 g/mole)
• 98.09 g/mole

12
Molecular Masses

• Can convert between mass and amount
• How many molecules are in a 10.0g sample of
  B(OH)3?

MW 61.8 g/mole 10g B(OH)3 x 1mole/61.8 g
0.162 mole B(OH) 3 0.162 mole B(OH)3 x 6.022
x 1023 molecules/mole 9.74 x
1022 molecules B(OH)3
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14
Ions

• loss of an electron yields a positively charged
  CATION.
• gain of an electron yields a negatively charged
  ANION.
• Two changes
• isotopes 14C 13C ---chemistry stays the same
• ions Na0 Na ---chemistries very
  different.

15
Common Monoatomic Ions

• Use the Periodic Table to determine charge.

16
Common Polyatomic Ions
Memorize These!
17
Ionic Compounds

• when cations () and anions (-) come together,
  they form neutral molecules called ionic
  compounds.
• ions do not exist by themselves in solid state,
  only in solution.
• Ca2 2Cl- -----gt CaCl2
• Na Cl- -----gt NaCl
• 3Ca2 2PO4-3 -----gt Ca3 (PO4 )2

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19
How Do We Know How Many in a Mole?
From X-Ray Crystallography 4NaCl molecules
per unit cell Volume 1.78 x 10-22 cm3
Density of NaCl 2.17 g/cm3 From Mass
Spectrometry 1Na 22.99 amu 1 Cl
35.45 amu 1NaCl 58.44 amu Define MW same
value as amu, but in g/mole (58.44 g/mole for
NaCl)
20
How Do We Know How Many in a Mole?
From X-Ray Crystallography 4NaCl molecules
per unit cell Volume 1.78 x 10-22 cm3
Density of NaCl 2.17 g/cm3 From Mass
Spectrometry 1Na 22.99 amu 1 Cl
35.45 amu 1NaCl 58.44 amu Define MW same
value as amu, but in g/mole (58.44 g/mole for
NaCl) 4 molecules 1 unit cell
1cm3 58.44g x
x x
unit cell 1.78 x 10-22
cm3 2.17g mole
21
How Do We Know How Many in a Mole?
From X-Ray Crystallography 4NaCl molecules
per unit cell Volume 1.78 x 10-22 cm3
Density of NaCl 2.17 g/cm3 From Mass
Spectrometry 1Na 22.99 amu 1 Cl
35.45 amu 1NaCl 58.44 amu Define MW same
value as amu, but in g/mole (58.44 g/mole for
NaCl) 4 molecules 1 unit cell
1cm3 58.44g x
x x
6.02 x 1023 molecules/mole unit
cell 1.78 x 10-22 cm3 2.17g
mole
22
Elements as Molecules
sulfur
S8
seven diatomic gases
23
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