1. The Atom and You
(What are we made of?)

2. Page 3

3. Early Greek Theories 400 B.C.
Democritus thought matter could not be divided indefinitely.
Called the smallest particle ‘Atomos’
Democritus
Atom - Smallest particle of an element that retains the chemical identity of that element

4. Comparison World population: 7,000,000,000*
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Comparison
World population: 7,000,000,000
Atoms in Cu penny: 29,000,000,000,000,000,000,000 *

5. John Dalton 1800 -Dalton proposed a modern atomic model
based on experimentation not on pure reason.
All matter is made of atoms.
Atoms of an element are identical.
Atoms of different elements combine in constant ratios to form compounds.
Atoms are rearranged in reactions.
His ideas account for the law of conservation of mass (atoms are neither created nor destroyed) and the law of constant composition (elements combine in fixed ratios).

6. Negative particles in a positive matrix.
J.J. Thomson (1897)
Applied electric and magnetic fields to cathode rays and got particles that shot off.
These particle were negative, electrons.
“Plum pudding” model of the atom
Negative particles in a positive matrix.
V.Montgomery & R.Smith

7. Ernest Rutherford Rutherford shot alpha () particles at gold foil.
Zinc sulfide screen
Thin gold foil
Lead block
Radioactive substance
path of invisible -particles
Most particles passed through. So, atoms are mostly empty.
Some positive -particles deflected or bounced back!
Thus, a “nucleus” is positive & holds most of an atom’s mass.

8. Bohr’s model
Electrons orbit the nucleus in “shells”
Proposed that electrons must have enough energy to keep them in constant motion around the nucleus
Analogous to the motion of the planets orbiting the sun
The further away, the more energy the electron has

9. Modern Model – Wave Mechanical Model (Electron Cloud)
Based on the work of many scientists
Protons (+) and neutrons (0) are in the nucleus
Electrons (-) are in an orbital (not an exact location of the electron, it is a probable place that the electron is located.
The thickest (most dense) part of the cloud is the most probable place of the electron - orbital

10. Wave Mechanical Model (Electron Cloud)

11. Regents Question: þ Subatomic particles can usually pass undeflected
through an atom because the volume of an atom
is composed of
(1) an uncharged nucleus
(2) largely empty space
(3) neutrons
(4) protons þ

12. Regents Question:
One model of the atom states that atoms are tiny particles composed of a uniform mixture of positive and negative charges. Scientists conducted an experiment where alpha particles were aimed at a thin layer of gold atoms.
Most of the alpha particles passed directly through the gold atoms. A few alpha particles were deflected from their straight-line paths. An illustration of the experiment is shown below.

13. Most of the alpha particles passed directly through the gold atoms undisturbed. What does this evidence suggest about the structure of the gold atoms?
A few of the alpha particles were deflected. What does this evidence suggest about the structure of the gold atoms?
How should the original model be revised based on the results of this experiment?
Most of the atom is empty space.
There is central + charge. The nucleus is +.
The atom is not a uniform mixture of + and - charge. Positive charge is located in a heavy central mass.

14. An orbital is the area of highest probability of finding an electron.
In the wave-mechanical model (electron cloud model), the electrons are in orbitals, which are defined as the regions of the most probable electron location (ground state).
An orbital is the area of highest probability of finding an electron.

15. Notes Now Take out paper. Atoms are made of smaller particles. Protons
Neutrons
Electrons

16. Subatomic Particles Symbol Location Charge Mass electron proton*
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Subatomic Particles
Symbol
Location
Charge
Mass
electron
proton
neutron *

17. Subatomic Particles e− p+ n Symbol Location Charge Mass electron*
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Subatomic Particles
Symbol
Location
Charge
Mass
electron e−
proton p+
neutron n *

18. Subatomic Particles e− p+ n Symbol Location Charge Mass electron*
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Subatomic Particles
Symbol
Location
Charge
Mass
electron e−
empty space
proton p+
nucleus
neutron n *

19. Subatomic Particles e− p+ n Symbol Location Charge Mass electron*
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Subatomic Particles
Symbol
Location
Charge
Mass
electron e−
empty space −1
proton p+
nucleus +1
neutron n *

20. Subatomic Particles e− p+ n Symbol Location Charge Mass electron*
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Subatomic Particles
Symbol
Location
Charge
Mass
electron e−
empty space −1
amu
proton p+
nucleus +1
1 amu
neutron n *

21. Regents Question: þ Which statement best describes electrons?
They are positive subatomic particles and are found in the nucleus.
They are positive subatomic particles and are found surrounding the nucleus.
They are negative subatomic particles and are found in the nucleus.
They are negative subatomic particles and are found surrounding the nucleus. þ

22. Regents Question:
In the modern model of the atom, each atom is composed of three major subatomic (or fundamental) particles.
Name the subatomic particles contained in the nucleus of the atom.
State the charge associated with each type of subatomic particle contained in the nucleus of the atom.
What is the net charge of the nucleus?
Proton and neutron
Proton is positive and the neutron is neutral
Positive

23. Regents Question: þ Which subatomic particle has no charge?
(1) alpha particle
(2) beta particle
(3) Neutron
(4) electron þ

24. Electron Configurations
Electron Configurations: arrangement of e- in an atom.
There is a distinct electron configuration for each atom in the ground state.
It is listed on the Periodic Table.

25. The ground state for Na is 2-8-1
The outermost electrons in an atom are called the valence electrons.
In general, the number of valence electrons affects the chemical properties of an element.
The ground state for Na is
The valence shell is the third shell.
The valence shell contains 1 electron.

26. Regents Question þ What is the total number of electrons in the
valence shell of an atom of aluminum in the
ground state? 8 2 3
(4) 10 þ

27. Regents Question: 06/02 #31
In which shell are the valence electrons of the elements in Period 2 found? 1 2 3 4 þ

28. Page 4 Find element on the Periodic Table.
Use the bolded number for number of electron. This is the Atomic Number.
The first shell can only contain 2 electron.
The next shells have electrons according to the formula 2n2.
Draw the correct number of shells and electrons

29. Sodium - Na Na is element number 11.
The bold number is 11, so the electrons equal 11.
First shell has 2.
The second has 8, so we need three shells.
Draw three circles an add the correct number of electrons.

30. Complete page 4, numbers 2-5.

31. Page 5

32. Notes Now
Take out paper.

33. Ions
When an atom, (neutral), gain or loses and electron it is known as an ION.
I do not drink GIN.
It makes my LIPs burn.

34. Ion Anion Cation atom with an electrical charge*
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Ion
atom with an electrical charge
Anion
more electrons than protons: - charge
Cation
more protons than electrons: + charge *

35. Mg2+ 25 12 How many electrons, protons and neutrons? Anion or Cation?*
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How many electrons, protons and neutrons? 25
Mg2+ 12
Anion or Cation? *

36. Hf 4+ 179 72 How many electrons, protons and neutrons?*
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How many electrons, protons and neutrons?
179
Hf 4+ 72
Anion or Cation? *

37. Cl− 37 17 How many electrons, protons and neutrons? Anion or Cation? *
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How many electrons, protons and neutrons? 37
Cl− 17
Anion or Cation? *

38. Page 4

39. Sodium Ion – Na+1 Na is element number 11.
The bold number is 11, so the electrons equal 11. Take into account the charge.
+1 means one less electron. LIP – losing is positive. First shell has 2.
First shell has 2. The second has 8. There is no third shell.
Draw two circles an add the correct number of electrons.

40. Complete page 4, numbers 7-10.

41. Page 8

42. Review Time
Take out paper.

43. Atomic Particles

44. Atomic Number Mass Number Number of protons Number of positive charges
Number of electrons in a neutral atom
Mass Number
The mass of an atom (amu)

45. *
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How many electrons, protons and neutrons? 14 N 7 *

46. *
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How many electrons, protons and neutrons? 15 N 7 *

47. Isotopes
Atoms of the same element with the same atomic number but different mass number
Ex. Protium - Hydrogen proton =1
neutron = 0
Deuterium – Hydrogen proton = 1
neutron = 1
Tritium – Hydrogen proton = 1
neutron = 2

48. Mass number The number of protons plus neutrons in an atom*
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Mass number
The number of protons plus neutrons in an atom
Commonly follows chemical symbol: Ni-59 *

49. Iron-56 OR Fe-56 What has 5 protons and 6 neutrons?*
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How many electrons, protons and neutrons?
Iron-56 OR Fe-56
What has 5 protons and 6 neutrons? *

50. Page 11

51. Regents Question:
The number of neutrons in the nucleus of an atom can be determined by
Adding the atomic number to the mass number
Subtracting the atomic number from the mass number
Adding the mass number to the atomic mass
Subtracting the mass number from the atomic number þ

52. Regents Question:
The atomic number of an atom is always equal to the number of its
(1) protons, only
(2) neutrons, only
(3) protons plus neutrons
(4) protons plus electrons þ

53. Regents Question: þ What is the total number of protons in the
nucleus of an atom of potassium-42?
(1) 15
(2) 19
(3) 39
(4) 42
The mass number (42) is not necessary to find the number of protons. þ

54. Regents Question: þ The nucleus of an atom of K-42 contains
(1) 19 protons and 23 neutrons
(2) 19 protons and 42 neutrons
(3) 20 protons and 19 neutrons
(4) 23 protons and 19 neutrons þ

55. Regents Question:
An atom of carbon-12 and an atom of carbon-14 differ in
Atomic number
Atomic mass
Nuclear charge
Number of electrons þ
Carbon-12 and carbon-14 are isotopes.

56. Regents Question: þ All the isotopes of a given atom have
the same mass number and same atomic number
the same mass number but different atomic numbers
different mass numbers but the same atomic number
different mass numbers and different atomic number þ

57. Regents Question:
Atoms of the same element that have different numbers of neutrons are classified as
Charged atoms
Charged nuclei
Isomers
Isotopes þ

58. Take Out Periodic Table
What is the mass of the following:
H C Cl

59. Periodic Table Shows Atomic Mass

60. *
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Atomic Mass
average mass of an element’s atoms averaged according to their relative abundance
sum of relative abundances x isotope mass
WHAT? *

61. Atomic mass = 35.453 for Cl? (Shouldn’t it be a whole number?)*
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Why is:
Atomic mass = for Cl? (Shouldn’t it be a whole number?)
All elements have Isotopes *

62. Remember Isotopes Are Same element Different number of neutrons
Different Mass Numbers
Isotopes occur in different amounts
Remember Carbon Dating from Earth Science?

63. How do we calculate Atomic Mass? (AKA Average Atomic Mass)
Use the Mass number of the Isotopes.
Multiply that number by the percentage.
Add the resulting number together.
37 * .25 =
35 * .75 = 26.25
35.5

64. The average atomic mass of an element is the weighted average of the masses of its naturally occurring isotopes.
Isotope
Mass
Abundance
Calculation
12C 12
98.89%
12 x =
13C 13
1.108%
13 x =
Atomic Mass (weighted average)
12.01 amu

65. Regents Question:
The atomic mass of an element is calculated using the
(1) atomic number and the ratios of its naturally occurring isotopes
(2) atomic number and the half-lives of each of its isotopes
(3) masses and the ratios of its naturally occurring isotopes
(4) masses and the half-lives of each of its isotopes þ

66. Regents Question:
Hydrogen has three isotopes with mass numbers of 1, 2, and 3 and has an average atomic mass of amu. This information indicates that
Equal number of each isotope are present
More isotopes have an atomic mass of 2 or 3 than 1
More isotopes have an atomic mass of 1 rather than 2 of 3
Isotopes have only an atomic mass of 1 þ

67. Regents Question:
In which list are the elements arranged in order of increasing atomic mass?
Cl, K, Ar
Fe, Co, Ni
Te, I Xe
Ne, F, Na þ
Look for the masses on the periodic table of the elements.

68. Page 12

69. Notes Again
Take out paper

70. The Excited State
When an electron in an atom gains a specific amount of energy, the electron is at a higher energy state (excited state).

71. How is Sodium excited? Change the electron configuration
Normal electron configuration is
2-8-1
Possible excited states for Na are:
2-7-2
1-8-2

72. What are possible excited states for the following:
Hydrogen
Gold
Potassium
Chlorine
Magnesium
Manganese
Flourine

73. When an electron returns from a higher energy state to a lower energy state, a specific amount of energy is emitted. This emitted energy can be used to identify an element.
Emission Spectrum

74. Regents Question:
During a flame test, ions of a specific metal are heated in the flam of a gas burner. A characteristic color of light was emitted by these ions in the flame when the electrons
Gain energy as they return to lower energy levels
Gain energy as they move to higher energy levels
Emit energy as they return to lower energy levels
Emit energy as they move to higher energy levels þ

75. Regents Question:
When the electrons of an excited atom return to a lower energy state, the energy emitted can result in the production of
alpha particles
(2) Isotopes
(3) protons
(4) spectra þ

76. Regents Question:
Base your answers to the next two questions on the electron configuration table shown below.
What is the total number of valence electrons in an atom of electron configuration X?
Which electron configuration represents the excited state of a calcium atom?
Element Electron Configuration
X 2 –8 –8 – Y 2 –8 –7 – Z 2 –8 –8 2