History of the Atom

1
History of the Atom

• Scientists and Their Discoveries

2
Atoms

• Atoms- smallest possible unit into which matter
  can be divided, while still maintaining its
  properties.
• Made up of
• protons
• neutrons
• electrons
• Electrically they are NEUTRAL!!!!

-

For example, what is the smallest possible unit
into which a long essay can be divided and
still have some meaning?

-


-

-
-
3
Elements

• Element- made up of one kind of atom that cant
  be broken down into simpler substances by
  physical or chemical means
• 90 occur naturally on Earth
• 29 were synthesized (made) by scientists

4
The Periodic Table of Elements-Reference

• Periodic table tiles contain a lot of information
  and to understand it, its necessary to know the
  parts of the atom and some terminology concerning
  them

Atomic Number (number of protons)
8 O Oxygen 15.999
Element Symbol (a capital letter or a capital
followed by a lower case letter)
Element Name
Atomic Mass (weighted average of all isotopes
mass)
5
The Atoms Center

• Nucleons- particles in the nucleus of atoms
• Protons
• Neutrons

Notice that the electrons are not a part of the
nucleus
-
-
-
6
Neutrons

• Neutrons- neutral particles have no electric
  charge
• Help make up the nucleus of the atom
• Contribute to the atomic mass
• 1.67 X 10-24 g

7
Protons ()

• Protons- positively charged particles
• In nucleus
• They ID an atomatomic number
• Contribute to the mass of the atom 1.67 X 10-24
  g
• Charge 1.6 X 10-19 coulombs (same value as
  electron but positive)

8
Atomic Number

• Atomic number - the number of protons in the
  nucleus of an atomits ID !!!!
• Represented by Z

-
-
-
What would be the atomic number of the atom to
the left? What element is it?
9
Electrons (-)

• Electrons- negatively charged particles
• Outside the nucleus of the atom in electron
  orbits/levels
• Move rapidly and create an electron cloud
• Mass is insignificant
• Valence electrons- the outermost electrons
  involved in the formation of chemical bonds

-
10
Neutral Atoms

• Most atoms are neutral and the number of protons
  the number of electrons
• 1 protons and 1 electrons0 (neutral)
• Atomic number protons electrons

11
Electromagnetic Force

• Electromagnetic force is the force that results
  from the repulsion of like charges and the
  attraction of opposites
• AND NEUTRALIZE
• ONE ANOTHER
• This the force that holds the electrons around
  the nucleus
• Bill Nye Atoms

-
-
-
Notice how the particles with the same charge
move apart and the particles with different
charges move together.
Why are neutrons not pictured above?
12
Atomic Models

• Model a familiar idea used to explain
  unfamiliar facts observed in nature
• Theory- an explanation of observable facts and
  phenomena
• To remain valid, models and theories must
• Explain all known facts
• Enable scientists to make correct predictions

13
Democritus(460 BC 370 BC)

• Proposed the existence of atoms from Greek word
  atomos which means not to cut or
  indivisible
• Thought you could cut matter in half until you
  got an indivisible (not dividable) particle

Image taken from https//reich-chemistry.wikispac
es.com/T.GlennTimeLineProject
14
Aristotle(384 BC 322BC)

• Rejected idea of the atom
• Said matter could be cut continually
• Aristotle was more influential than Democritus
  so atoms were forgotten about until late 1700s

15
Antoine Lavoisier (1743 1794)

• Father of Modern Chemistry
• Generated a list of 33 elements
• Devised the metric system
• Discovered/proposed the Law of Conservation of
  Mass
• - matter cant be created or destroyed, it just
  changes form (beginning mass end mass)

Image taken from www.ldeo.columbia.edu/.../v1001/
geotime2.html
16
John Dalton (1766 1844)

• In 1803 he proposed first experimentally based
  Atomic Theory that states atoms
• are building blocks of matter
• are indivisible
• of the same element are identical
• of different elements are different
• Billiard Ball Model

17
John Dalton (1766 1844)

• Daltons Atomic Theory also explained The Law of
  Multiple Proportions -ratio of the masses of
  combined elements are WHOLE numbers which become
  subscripts for chemical formulas
• Nitrogen and Oxygen combine to form NO or NO2,
  but not NO1.5

18
Law of Definite Composition

• Law of Definite Composition (Prousts Law)-
  elements combine in a definite (constant) ratio
  by atomic mass
• Water (H2O) is always 2 hydrogens for each oxygen
• 162 oxygenhydrogen mass ratio or 81 reduced
• For Carbon dioxide (CO2) there is always a 3212
  oxygen to carbon mass ratio, or 83 reduced.

19
J.J. Thomson (1856 1940)

• Put electricity through a vacuum tube and
  produced a beam that was negatively charged
• Cathode Ray Tube Experiment

20
J.J. Thomson (1856 1940)

• Credited with discovery of electron a blow to
  Daltons indivisible atom idea
• Plum Pudding Model
• Also because atoms are neutral, the negative
  electrons must be embedded in a ball of positive
  charge

21
Millikan Oil Drop Experiment

• Calculated the mass and quantified the charge of
  electrons!
• Mass of electron 9.1 X 10-28 grams
• (0.00000000000000000000000000091 g)
• Charge on the electron -1.6 X 10-19 coulombs
  (unit of charge)
• Millikan Animation and Interactive

22
Millikan Oil Drop Experiment-Reference
23

JJ Thomson and E. Goldstein

• Realized if neutral atoms contain negative
  electrons, they must contain positive particles
• Used vacuum tube similar to discovery of electron
  to discover protons
• Mass 1.67 X 10-24 grams (much heavier than
  electron!)
• Charge 1.6 X 10-19 coulombs (same value as
  electron but positive)

24
Ernest Rutherford (1871 1937)

• Gold-foil experiment
• Positively charged alpha particles aimed at thin
  gold foil, but most passed through
• A few were deflected and some even bounced right
  back
• Gold foil experiment

25
Rutherfords Gold Foil Experiment-Reference
(1871 1937)
26
Ernest Rutherford (1871 1937)

• Conclusions
• Disproved Thomson because showed most of atom is
  empty space
• Discovered dense, positively charged core, or
  nucleus, repels the alpha particles
• Protons are surrounded by negatively charged
  electrons
• Planetary Model
• Youll never see life the same way again

27
James Chadwick (1891 1974)

• Discovered the atomic mass of most elements was
  double the number of protons ? discovery of the
  neutron in 1932
• Worked on the Manhattan Project
• Worked with Ernest Rutherford
• Like many others before him, he won a Nobel Prize

28
ReviewEarly Atomic Theory video 5 min

• Number your paper from 1-5 and answer the
  following questions. Two will be cumulative
  review!
• 1. Which of these has 3 significant figures?
• a. 3340
• b. 3.340
• c. 0.001334
• d. 334.00

29
Review

• A
• 2. Which of these is a homogenous mixture?
• a. salt
• b. iced tea
• c. pizza
• d. your computer

30
Review

• B
• 3. Which of these is true about subatomic
  particles?
• a. electrons are negatively charged and in the
  nucleus
• b. protons are negatively charged and in the
  nucleus
• c. protons are positively charged and fly around
  the outside of the nucleus
• d. neutrons are neutral and are in the nucleus

31
Review

• D
• 4. Which of these is true about the discovery of
  Millikans oil drop experiment
• a. He discovered the electron
• b. He discovered the mass of the neutron
• c. He discovered the mass and the charge of the
  electron
• d. He discovered the proton

32
Review

• C
• 5. Which of these is false?
• a. Neutrons are neutral
• b. Protons are positive and two will repel
• c. Electrons are negative and two will attract
• d. Protons are positive and they will attract
  negative electrons

33
Review

• C

34
Mass of Sub-Atomic Particles-Reference
(protons, neutrons, electrons)
Neutron 1.6749286 x10-24 gProton 1.6726231
x10-24 gElectron 9.1093897 x10-28 g
1836 electrons 1 proton
1839 electrons 1 neutron
How do you think the mass of a neutron compares
to that of a proton?
1 neutron 1 proton 1.67 x10-24 g
35
Mass Number

• Mass number number of particles of significant
  mass in the atom
• Represented by A
• protons neutrons mass number
• Electrons are NOT included, their mass is zero
• NOT found directly on the periodic table!

Particle Charge Mass number Location in atom
Proton 1
Neutron 1
Electron 0
36
Lets Do It!!!
What would be the mass number of this atom?
-

? 3
? 4
-
3 protons 4 neutrons a mass number of 7
Why did we not account for the electrons when
calculating the mass number?
-
37
Calculating the Actual Mass of 1 Atom

• Actual mass of an atom is determined by the
  protons and neutrons (electrons have virtually no
  mass)
• Each proton and neutron mass 1.67 x 10-24 g
• Ex a hydrogen atom has 1 electron and 1 proton
• Proton 1.67 x10-24 g
• No neutrons 0g
• Electron 0 g
• Mass of the entire hydrogen atom 1.67 x10-24 g

38
Calculating the Actual Mass of 1 Atom-Reference

• The actual mass of an atom
• (protons neutrons)(mass of ps and
  ns)(protons neutrons) (1.67 x 10-24 g)
• dont count sds
• Ex Whats the actual mass of a Lithium atom with
  3 protons and 4 neutrons?
• (protons neutrons)(mass of ps and ns)
• (7)(1.67 x
  10-24g)
• 
  1.17 x 10-23 g

39
Relate Actual Mass to Mass Number

• We can say the actual mass of an atom
• (protons neutrons)(mass of ps and ns)
• OR
• (mass number) (1.67 x 10-24 g)
• dont count sds

40
Lets Do It!!!

• Whats the actual mass of a Carbon atom with 6
  protons and 8 neutrons?

41
Lets Do It!!!

• (14)(1.67 x 10-24g) 2.34 x 10-23 g

42
Calculating the Actual Mass of 1 Atom

• Actual mass of an atom based on the idea that the
  whole atom is equal to the sum of the parts
• Not exactly correct because binding energy is
  needed to hold the parts of an atom together
• Some mass converted to this binding energy in a
  nuclear reaction so the calculation gives a value
  that is a little larger than reality
• (E mc2)

43
Isotopes

• What mass numbers do these atoms have?
• What elements are these?
• How do you know?

44
Isotopes

• There mass numbers are 1, 2, and 3 but they all
  have one proton and therefore are all hydrogen!
• So what is going on? They are isotopes.

45
Isotopes

• Isotopes different versions of atoms of an
  element that have same of protons but different
  of neutrons
• This discovery disproved one of Daltons idea
  that atoms of the same element are exactly alike!

46
Isotopes

• Hydrogen-1 (Protium) 1 proton, no neutrons and
  is most common
• Hydrogen-2 (Deuterium) 1 proton and 1 neutron
• Hydrogen-3 (Tritium) 1 proton and 2 neutrons
• All versions of hydrogen!

47
Hyphen Notation-Reference

• We use mass numbers to distinguish between
  isotopes because they differ in their number of
  neutrons
• Hydrogen-1 1 proton 0 neutronmass 1
• Hydrogen-2 1 proton 1 neutron mass 2
• Hydrogen-3 1 proton 2 neutronsmass 3
• This is written in hyphen notation

48
Nuclear Symbols-Reference

• Nuclear symbols are a way to write atoms using
  the mass number and atomic number
• Format
• Hydrogen-1 Hydrogen-2 Hydrogen-3
• 1 2
  3
• H H
  H
• 1 1
  1
•  

49
Lets Do It!!!

• Naturally occurring carbon consists of three
  isotopes, Carbon-12, Carbon-13, and Carbon-14.
  State the number of protons, neutrons, and
  electrons in each of these carbon atoms
• Think-Pair-Share
• 12C 13C 14C
• 6 6
  6
• p _______ _______
  _______
• n _______ _______
  _______
• e _______ _______
  _______

50
ReviewAtomic Number video 9 min

• Number your paper from 1-5 and answer the
  following questions. Two will be cumulative
  review!
• 1. Which of these is proper scientific notation?
• a. 4.56 X 106
• b. 4.5 X 32
• c. 45.6 X 1010
• d. 456 X 106

51
Review

• A
• 2. Which of these would be the correct answer
  with the proper number of significant digits if
  you multiplied 0.05 X 3.01
• a. 0.1505
• b. 0.150
• c. 0.15
• d. 0.2

52
Review

• D Remember beginning zeros are never significant,
  so 0.05 has only 1!
• 3. What does this mean? 14C
  6
• a. this atom has 6 neutrons and 20 electrons
• b. this atom has 6 protons and 8 neutrons for a
  combined mass number of 14
• c. this atom has 6 protons and 14 electons
• d. this atoms has 6 electrons and 14 neutrons

53
Review

• B
• 4. Which of these is a correct definition of an
  isotope?
• a. different versions of an element that have a
  different number of neutrons
• b. atoms of the same element with the same atomic
  number but different mass number
• c. different version of an element that have the
  different number of electrons
• d. A and B
• e. B and C

54
Review

• D
• 5. How do you calculate the actual mass of an
  atom
• a. add up all the protons, electrons, and
  neutrons
• b. add up all the protons and neutrons and divide
  by two
• c. add up all the protons and neutrons and
  multiply by 1.67 x 10-24 g
• d. add up all the protons and neutrons

55
Review

• C

56
Actual Mass of 1 Atom-Reference

• The actual mass of an atom is a super small
  number and is cumbersome in calculations, so
  scientists assigned a relative scale to the mass
  of these particles and created a new unit called
  atomic mass unit, or amu (?)
• amu (?) atomic mass unit

57
Finding Atomic Mass of a Single Atom

• To convert from actual mass to this new amu,
  scientists set Carbon as the standard and the
  value of the amu unit is defined by the actual
  mass of Carbon-12
• Actual mass of C-12 (12)(1.67x10-24g)
  2.00x10-23g
• and we use this as a standard to create a
  conversion factor
• 2.00x10-23g 12? (amu)

58
Reference-Atomic Mass of a Single Atom

• Find the atomic mass of an Oxygen-18 atom
• Step 1 calculate the actual mass of an
  Oxygen-18 atom
• 18 x 1.67x10-24 g 3.01 x10-23 g
• Step 2 use dimensional analysis to convert to
  amu with our Carbon standard conversion factor
• 3.01 x10-23 g x 12 ? 18.1 amu
• 2.00 x10-23 g
• Dont use 12 when figuring SDs because it is a
  standard, not a measurement

59
Lets Do It!!!

• Whats the atomic mass of a 7 Li atom?

60
Lets Do It!!!

• Whats the atomic mass of a 7 Li atom?
• Step 1 calculate the actual mass of this lithium
  atom
• 7 x 1.67x10-24 g 1.17 x10-23 g
• Step 2 use dimensional analysis to convert to
  amu with our Carbon standard conversion
• 1.17 x10-23 g x 12 ? 7.02 amu
• 2.00 x10-23 g

61
Isotopes

• What elements are these?
• What are their mass numbers?

62
Isotopes

• How would we write the hyphen notation of these
  isotopes? Nuclear notation?
• Students on board

63
Isotopes

• If we pick up one of the trillions of boron atoms
  in the world, it could be either of these 2 types
  because they are both present

• Boron-10
  Boron-11

64
Isotopes

• As it turns out, any mass of Boron, and all Boron
  in the world, is 20 Boron-10, and 80
  Boron-11their relative abundances

• Boron-10
  Boron-11
• 20
  80

65
Isotopes

• Many elements are like this
• All chlorine in the world is 75 Chlorine-35 and
  25 Chlorine-37
• The majority are Chlorine-35

66
Isotopes-Reference

• In nature there are always mixtures of isotopes
  and this can pose difficulties when we do
  calculations. Why?
• Pencil lead (carbon) has some carbon-12,
  carbon-13 and carbon-14 mixed
• The mass of one Carbon-12 atom with 12 protons
  and neutrons would be this
• (12)(mass of protons and neutrons)
• (12)(1.67 x10-24 g) 12 amus (?)
• but that is just for Carbon-12!!

67
Isotopes and Atomic Mass of an Element

• STOP! Mass confusion and Reference Chart
• In calculations we need a mass value that
  represents the whole element mixture (carbon-12,
  carbon-13 and carbon-14 mixed), not just one
  isotope, like Carbon-12 How?

68
Atomic Mass of an Element-Reference

• Atomic mass- WEIGHTED average of the atomic
  masses of all the elements isotopes as they are
  found in nature (dont confuse it with mass
  number which is just p n)
• (abundance isotope 1) (atomic mass isotope 1 ?)
  
• (abundance isotope 2) (atomic mass isotope 2 ?)
  
• continue for all isotopes

69
Isotopes and Atomic Mass of an Element

• The atomic masses of each element (the weighted
  average of all its isotopes) is found in the
  periodic table

• Boron-10
  Boron-11
• 20
  80

70

• Atomic Mass of an Element Reference
• Use the following data to calculate the atomic
  mass for the element Magnesium
• Isotope Atomic Mass of Isotope Abundance
• Mg - 24 23.982628 ? 78.600
• Mg - 25 24.963745 ? 10.11
• Mg - 26 25.960802 ? 11.29
  (.78600) (23.982628 ? )
• (.1011) (24.963745 ? )
• (.1129) (25.960802 ? ) 18.850 ? 2.52
  ? 2.931 ? 24.305 ?
• You do SDs for every individual calculation

71
Lets Do It!!!!

• The element copper has naturally occurring
  isotopes with mass numbers of 63 and 65
• The relative abundance and atomic masses are
  69.2 for a mass of 62.93amu and 30.8 for a mass
  of 64.93amu. Calculate the atomic mass of the
  element copper

72
Lets Do It!!!!

• Divide the percentages by 100 to convert to
  decimals
• (.692) (62.93amu) (.308)(64.93amu)
• 43.5 amu 20.0 amu
• 63.5 amu
• This shows that the majority of the isotopes
  found in nature are 62.93 amu (closer to 63 than
  65)

73
Lets Do It!!!

• There are two isotopes of silicon. The atomic
  mass of the element silicon found on the periodic
  table is 28.086amu.
• Which of these is not possible to be one of the
  atomic masses of the individual isotopes?
• A. 26.065
• B. 29.543
• C. 28.086
• D. 27.439
•  

74

• Atomic Mass of an Element
• If an element has only 1 isotope, then the atomic
  mass of that isotope IS the atomic mass of the
  element

75
Review

• Number your paper from 1-5 and answer the
  following questions. Two will be cumulative
  review!
• 1. Which of these is the symbol for the metric
  unit micro (and also for amu)?
• A. M
• B. m
• C. ?
• D. µ

76
Review

• D
• 2. Which of these is the amount of protons in an
  atom and therefore, the ID.
• a. atomic mass
• b. atomic number
• c. mass number
• d. isotope number

77
Review

• B
• 3. What is the bottom number on this periodic
  table tile?
• a. atomic mass of the element
• Boron
• b. atomic number
• c. mass number
• d. atomic mass of a Boron atom

78
Review

• A
• 4. The atomic mass of the element sulfur is 32.1
  g. There are four common isotopes of sulfur, S-32
  (32.2344 µ), S-33 (33.45676 µ), S-34 (34.15643
  µ), S-36 (36.44321 µ) Which of these isotopes
  is the most abundant?
• a. S-32
• b. S-33
• c. S-34
• d. S-35

79
Review

• A
• 5. How do you calculate the atomic mass of an
  element?
• a. l x w x h
• b. D m/V
• c. (abundance isotope 1)(atomic mass 1)
  (abundance isotope 2) (atomic mass 2) etc.
  
• d. mass number atomic number

80
Review

• C

81
The Mole

• The word mole in Chemistry is a term used to
  describe a certain amount of something
• For example
• 1 dozen 12
• 1 bakers dozen 13
• 1 gross 144
• 1 mole 6.02 X 10 23 which is
• 602,000,000,000,000,000,000,000 or 602
  hextrillion of whatever

82
The Mole-Reference

• A mole is the amount of a substance that contains
  6.02 x 1023 of something
• 1 mole of pencils 6.02 x 1023 pencils
• 1 mole of eggs 6.02 x 1023 eggs
• 1 mole of carbon 6.02 x 1023 carbon atoms
• 6.02 x 1023 is called Avogadros number
• It helps us count atoms, which we cant see,
  using the measurement of mass

83
Lets Do It!!!

• How many atoms of oxygen are in a mole of oxygen?
• How many atoms of magnesium are in a mole of
  magnesium?
• Would they have the same mass?

84
Atomic Mass of an Element Mole-Reference

• Each element has a unique atomic mass and this is
  a standard for each element
• Atomic mass mass of 1 mole of an element
• The atomic masses are from the periodic table and
  we use grams
• 1 mole O 6.02 x 1023 atoms O 15.999 g O
• 1 mole Mg 6.02 x 1023 atoms Mg 24.305 g Mg

85
Molar Mass

• Molar mass mass of 1 mole of a pure substance
• Molar mass of element (g/mol) the atomic mass
  of an element
• Molar mass of a compound (g/mol)- the sum of the
  molar masses of the elements making up the
  compound
• Whats the molar mass of Cl? Dont forget units!
  We are going to round to 3 SDs for the atomic
  mass
• Whats the molar mass of H2O?

86
Moles to Atoms-Reference

• 1 mole 6.02x1023 atoms atomic mass (g)
• These can be used as a conversion factors
  6.02 x 1023 atoms 1 mole atomic mass
• atomic mass 6.02 x 1023 atoms 1
  mole
• If you have 1.5 moles of potassium, how many
  atoms is this?
• Question mark format for DA
• ? atoms of K

6.02 x 1023 atoms K ---------------------
1 mole K
9.03 x 1023 atoms K
1.50 mole K
87
Moles to Grams-Reference

• 1 mole 6.02x1023 atoms Atomic Mass (g)
• If you have 1.25 moles of potassium, how many
  grams is this?
• Question mark format for DA
• ? grams of K

1.25 moles K
39.1 g K ----------- 1 mole K
48.9 g K
88
Grams to Atoms-Reference

• 1 mole 6.02x1023 atoms Atomic Mass (g)
• If you have 12.5 grams of phosphorus, how many
  atoms is this?
• Question mark format for DA
• ? atoms of P

6.02 x 1023 atoms P x ---------------------
31.0 g P
12.5 g P
2.43 x 1023 atoms P
89
Lets Do It!!

• 1 mole 6.02x1023 atoms Atomic Mass (g)
• If you have 2.93 x 1024 atoms of sodium, how many
  moles is this?
• Question mark format for DA
• ? moles of Na

2.93 x 1024 atoms Na
4.87 moles Na
90
Lets Do It!!!

• 1 mole 6.02x1023 atoms Atomic Mass (g)
• If you have 1.25 grams of sodium, how many moles
  is this?
• Question mark format for DA
• ? moles of Na

1 mole Na -------------- 23.0 g Na
1.25 g Na
0.0543 mole Na
91
Lets Do It!!!

• 1 mole 6.02x1023 atoms Atomic Mass (g)
• If you have 3.52 x 1022 atoms of carbon, how
  many grams is this?
• ? grams of C

12.0 g C x
---------------- 6.02 x 1023 atoms C
3.52 x 1022 atoms C
.702 g C
92
Mole vs. Molecule

• Dont confuse mole and molecule
• A mole is an amount
• A molecule is a thing
• We can have a mole of molecules
• A mole of water molecules
• 6.02 x 1023 molecules of water
• If I have an amino acid molecule tryptophan,
  C11H12N2O2, how many molecules of tryptophan are
  in a mole?

93
Review

• Number your paper from 1-5 and answer the
  following questions. Two will be cumulative
  review!
• 1. Which of these is proper scientific notation?
• a. 5.56 X 106
• b. 3.5 X 32
• c. 95.6 X 1010
• d. 256 X 106

94
Review

• A
• 2. Which of the numbers in the nitrogen periodic
  table tile is the atomic number?
• a. N
• b. 14
• c. 14.007
• d. 7

95
Review

• D
• 3. Which of these is NOT a correct conversion
  factor for Carbon?
• a. 1 mole C
• 6.02 x 1023 g C
• b. 1 mole C
• 6.02 x 1023 atoms C
• c. 1 mole C
• 12.011 g C
• d. 12.011 g C
• 6.02 x 1023 atoms C

96
Review

• A
• 4. If I have 14.007 grams of nitrogen, how many
  atoms do I have?
• a. 1.67 x10-24
• b. 1.17 x10-23
• c. 2.24 x10-23
• d. 6.02x1023

97
Review

• D
• 5. How many atoms are in 10 moles of carbon?
• a. 10 atoms
• b. 6 atoms
• c. 6.02x1023 atoms
• d. 6.02x1024 atoms

98
Review

• D
• 1 mole of ANYTHING 6.02x1023 atoms
• ? Atoms 10 moles C x 6.02x1023 atoms C
• 1
  mole C
• 10 x 6.02x1023 atoms C 6.02x1024 atoms

99
Radius of Nucleus of an Atom-Reference

• Radius (1.4 x 10-13 cm)
• Where A mass number of the atom
• of protons neutrons
• and the cube root of the mass
  number
• and 1.4 x 10-13 cm a constant that
• 
  describes the
• effective
  range of force

100
Radius of Nucleus of an Atom-Reference

• Calculate the radius of the nucleus of a 56Fe
  atom
• Radius (1.4 x 10-13 cm)
• Radius (1.4 X 10-13 cm)
• Radius 5.4 X 10-13 cm
• only round ONCE ! ! !

101
Volume of a Nucleus-Reference

• Calculate the volume of the nucleus of a 56Fe
  atom (we model as a sphere)
• Volume of a sphere
• Volume
• Volume 6.6 10-37 cm3

102
Size of the Nucleus
Atom Nuclear Radius (1.4 x 10-13 cm) Nuclear Volume Nuclear Mass A(1.6710-24g ) Nuclear Density





103
Size of the Nucleus
Atom Nuclear Radius (1.4 x 10-13 cm) Nuclear Volume Nuclear Mass A(1.6710-24g ) Nuclear Density
4.0 x 10-13 cm
8.1 x 10-13 cm
2.2 x 10-13 cm
5.6 x 10-13 cm
6.0 x 10-13 cm
104
Size of the Nucleus
Atom Nuclear Radius (1.4 x 10-13 cm) Nuclear Volume Nuclear Mass A(1.6710-24g ) Nuclear Density
4.0 x 10-13 cm 2.7 x 10-37 cm3
8.1 x 10-13 cm 2.2 x 10-36 cm3
2.2 x 10-13 cm 4.5 x 10-38 cm3
5.6 x 10-13 cm 7.4 x 10-37 cm3
6.0 x 10-13 cm 9.0 x 10-37 cm3
105
Size of the Nucleus
Atom Nuclear Radius (1.4 x 10-13 cm) Nuclear Volume Nuclear Mass A(1.6710-24g ) Nuclear Density
4.0 x 10-13 cm 2.7 x 10-37 cm3 3.84 x 10-23g
8.1 x 10-13 cm 2.2 x 10-36 cm3 3.29 x 10-22g
2.2 x 10-13 cm 4.5 x 10-38 cm3 6.68 x 10-24g
5.6 x 10-13 cm 7.4 x 10-37 cm3 1.07 x 10-22g
6.0 x 10-13 cm 9.0 x 10-37 cm3 1.34 x 10-22g
106
Size of the Nucleus-Reference
Atom Nuclear Radius (1.4 x 10-13 cm) Nuclear Volume Nuclear Mass A(1.6710-24g ) Nuclear Density
4.0 x 10-13 cm 2.7 x 10-37 cm3 3.84 x 10-23g 1.4 x 1014 g/cm3
8.1 x 10-13 cm 2.2 x 10-36 cm3 3.29 x 10-22g 1.5 x 1014 g/cm3
2.2 x 10-13 cm 4.5 x 10-38 cm3 6.68 x 10-24g 1.5 x 1014 g/cm3
5.6 x 10-13 cm 7.4 x 10-37 cm3 1.07 x 10-22g 1.5 x 1014 g/cm3
6.0 x 10-13 cm 9.0 x 10-37 cm3 1.34 x 10-22g 1.5 x 1014 g/cm3
107
Densities of Atoms

• Why are these density values nearly the same?
• Because all nuclei are made up of the same
  material (protons neutrons). The SAME material
  always has the SAME density!

108
Densities of Atoms

• If we look up the density of the element sodium
  (its on some periodic tables) we see that its
  density is .971 g/cm3.
• Why is this different from the value we
  calculated?
• We calculated values for the nucleus only and the
  periodic tables value is for the whole atom
  including the space that the electrons occupy