1. The Physical Setting Chemistry Day 1 slides 3-11 Day 2 slides 12-26

2. I. Atomic Concepts

3. The modern model of the atom has evolved over a long period of time through the work of many scientists.
Democritus – matter is made up of particles called atoms
Dalton – atoms of the same element are alike – solid indivisible spheres
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4. Thomson – discovers electrons – plum pudding model
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5. Bohr – electrons orbit the nucleus
Rutherford – gold foil experiment – discovers heavy, + charge nucleus – mostly empty space
Bohr – electrons orbit the nucleus
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6. Regents Question: 08/02 #1
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
J Deutsch 2003

7. Regents Question: 01/03 #62-64
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.
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8. Regents Question cont’d
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.
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9. Regents Question: 06/03 #67
John Dalton was an English scientist who proposed that atoms were hard, indivisible spheres. In the modern model, the atom has a different internal structure.
Identify one experiment that led scientists to develop the modern model of the atom.
Rutherford’s gold foil experiment
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10. Regents Question cont’d
John Dalton was an English scientist who proposed that atoms were hard, indivisible spheres. In the modern model, the atom has a different internal structure.
Describe this experiment.
State one conclusion about the internal structure of the atom, based on this experiment.
Rutherford’s shot alpha particles a piece of gold foil. Most of the alpha particles went through, some were deflected and some were reflected.
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Most of the atom is empty space.

11. 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.
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12. Regents Question: 06/03 # 5
The region that is the most probable location of an electron in an atom is
(1) the nucleus
(2) an orbital
(3) the excited state
(4) an ion þ
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13. Regents Question: 06/02 #2
The modern model of the atom shows that electrons are
orbiting the nucleus in fixed paths
found in regions called orbitals
combined with neutrons in the nucleus
located in a solid sphere covering the nucleus þ
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14. Subatomic Particles: Mass Charge Part of the atom Symbol Mass charge
Proton
1 amu +1
Neutron
1amu
Electron o -1
Mass
Charge
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15. J Deutsch 2003

16. Each atom has a nucleus, with an overall positive charge, surrounded by one or more negatively charged electrons.
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17. Atomic Mass-number of nucleons (protons + neutrons)
Atomic number # of protons in the nucleus.
# neutrons = mass # - atomic #
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18. # of protons = # of electrons
Protons and electrons have equal but opposite charges. The number of protons equals the number of electrons in an atom. The atomic number for an element cannot change but its mass number can.
# of protons = # of electrons
Therefore, atoms are electrically neutral.
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19. Regents Question: 01/03 #1 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
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20. Regents Question: 08/02 #4
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
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21. Regents Question: 06/03 #36 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
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22. Regents Question: 06/03 #1
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
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23. Regents Question: 06/02 #33
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
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24. Regents Question: 06/03 #2 þ Which subatomic particle has no charge?
(1) alpha particle
(2) beta particle
(3) Neutron
(4) electron þ
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25. Subatomic particles contained in the nucleus include protons and neutrons.
Particles in the nucleus (protons and neutrons) are called nucleons
The mass of the atoms is concentrated in the nucleus
Electrons are not found in the nucleus, they are in orbitals around the nucleus.
The net charge of the nucleus is positive (+)
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26. Regents Question: 06/02 #58-60
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
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27. The ground state for Na is 2-8-1
valence electrons: The outermost electrons in an atom Importance: 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.
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28. If an atom gains or loses electrons it is called an ion.
When atoms gain electrons they become negative ions.
Flourine gains one electron it becomes F-1

29. When atoms lose electrons they become positive ions
Calcium loses 2 electrons it becomes Ca+2 ion
Gaining electrons is negative Losing electrons is positive GEN LEP
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30. Regents Question: 08/02 #2
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
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31. Regents Question: 06/03 #51-52
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
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32. Each electron in an atom has its own distinct amount of energy
Each electron in an atom has its own distinct amount of energy. Electrons in their lowest energy state are in the ground state.
Ground State electron configurations are found on the periodic table.
The ground state for Na is
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33. Regents Question: 06/02 #1
What is the electron configuration of a sulfur atom in the ground state?
2-4
2-6
2-8-4
2-8-6 þ
Look at the Periodic Table of the Elements
If you do not know the symbol for sulfur, check Table S
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34. Electron Configuration
The electron configuration for the ground state of an atom is given on the Periodic Table of the Elements.
Electron Configuration
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35. Possible excited states for Na are:
When an electron in an atom gains a specific amount of energy, the electron is at a higher energy state (excited state).
Possible excited states for Na are:
2-7-2
1-8-2
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36. 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
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37. Which element are part of the mixture?
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38. The maximum number of electrons in a principal energy level (shell) is 2n2.
Energy level (n)
Maximum number of electrons (2n2) 1 2 8 3 18 4 32
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39. Regents Question: 06/02 #31
In which shell are the valence electrons of the elements in Period 2 found? 1 2 3 4 þ
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40. Regents Question: 06/03 # 3
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
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41. Regents Question: 01/03 # 2
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
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42. Lewis dot Vs. Bohr Diagram
Lewis Dot diagrams only show the valence electrons
Bohr Diagrams show protons, neutrons and all shells of electrons
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43. Dots represent valence electrons
Dots represent valence electrons. Everything else (inner shell electrons and nucleus) is called the Kernel and is represented by the symbol.
Phosphorous has 5 valence electrons so we draw 5 dots around the symbol for phosphorous.
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44. It does not matter which side you start from.
The correct order to fill in the dots is to make a pair from the first 2 electrons then we fill in one on each side before we pair up. 1 2 Ne 5 3 8 6 4 7
It does not matter which side you start from.
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45. The correct order to fill in the dots is to make a pair from the first 2 electrons then we fill in one on each side before we pair up. 5 8 Ne 1 7 4 2 6 3
This will let you know how many electron pairs and how many unpaired electrons are in the atom’s valence shell
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46. Draw the Lewis Dot Structures of the first 18 elements.
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47. Atoms of an element that contain the same number of protons but a different number of neutrons are called isotopes of that element.
Isotopes of Hydrogen
1H – protium 1 proton 0 neutron
2H – deuterium 1 proton 1 neutron
3H – tritium 1 proton 2 neutrons
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48. The number of protons in an atom (atomic number) identifies the element. 6C The sum of the protons and neutrons in an atom (mass number) identifies an isotope.Common notations that represent isotopes include: 14C, carbon-14, C-14.
Atomic number is written on the bottom left.
Mass number is written on the upper left.
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49. Here are three isotopes of an element: 612C 613C 614C
The element is:
The number 6 refers to the
The numbers 12, 13, and 14 refer to the
How many protons and neutrons are in the first isotope?
How many protons and neutrons are in the second isotope?
How many protons and neutrons are in the third isotope?  
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50. Regents Question: 01/03 #9
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.
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51. Regents Question: 06/02 #4 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
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52. Regents Question: 06/02 #9
Atoms of the same element that have different numbers of neutrons are classified as
Charged atoms
Charged nuclei
Isomers
Isotopes þ
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53. Electron Configuration tells us how many electrons in each principal energy level (shell).
Atomic Number = 7
Mass Number = 14
7 protons
7 neutrons
7 electrons
Electron configuration: 2-5
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54. 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
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55. Regents Question: 06/03 # 4
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
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56. Regents Question: 01/03 #36
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
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57. Regents Question: 01/03 #9
An atom of carbon-12 and an atom of carbon-14 differ in
Atomic number
Atomic mass
Nuclear charge
Number of electrons þ
J Deutsch 2003

58. Regents Question: 06/02 #4 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
J Deutsch 2003

59. Regents Question: 06/02 #9
Atoms of the same element that have different numbers of neutrons are classified as
Charged atoms
Charged nuclei
Isomers
Isotopes þ
J Deutsch 2003

60. Regents Question: 01/03 #36
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
J Deutsch 2003

61. Regents Question: 01/03 #3
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.
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