Atomic Structure and the Periodic Table

1
Chapter 3

• Atomic Structure and the Periodic Table

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Sec 3.1 Internal Structure of Atom

• Subatomic particles (smaller than atom)
• Proton(P) Charge of 1 Mass of 1 (amu)
• Neutron(N) Charge of 0 Mass of 1
• Electron(e) Charge of -1 Mass of 0.0005

Similar Table on on page 48
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Sec 3.1 Internal Structure of Atom

• Atomic mass units (amu)
• 1 amu 1.6605X10-25 grams
• Like charges repel, opposites attract
• Overall the charge of an atom is neutral (0)
• Thus Protons must be equal to Electrons

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Sec 3.1 Internal Structure of Atom

• Nucleus tight cluster in the center of the atom
  containing the P and N
• Electrons move around the nucleus
• 99 of the mass of an atom in the nucleus

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Sec 3.2 Atomic Number Mass Number

• Atomic number number of protons in an atom
• Mass number the sum of the protons and neutrons
  in an atom
• Mass P N
• Since 99 of the mass of an atom is in the
  nucleus this is appropriate
• Neutrons Mass number Atomic Number

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Sec 3.2 Atomic Number Mass Number

• Arrangement on periodic table
• Atomic is a whole number generally above the
  symbol
• Mass is a decimal generally below the symbol
• Revised definition of element
• A pure substance in which all atoms present have
  the same atomic number

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Sec 3.3 Isotopes Atomic Masses

• Isotopes the number of neutrons can change and
  still maintain the identity of the element.
  Examples Carbon-13 or Hydrogen-2 (deuterium)
• Isotopes of an element have a different mass
  number but the same atomic number
• Isotopes still remain neutrally charged

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Sec 3.3 Isotopes Atomic Masses

• Isotopes are written with two numbers to the left
  of the symbol
• The atomic number is written as a subscript (XC)
• The mass number is written as a superscript (YC)
• Many elements exist in nature as a mixture of
  isotopes
• The atomic weight (atomic mass) for an element is
  a weighted average of the masses of the isotopes

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Sec 3.3 Isotopes Atomic Masses

• Example Chlorine exists as Cl-35 75.53 and
  Cl-37 24.47
• Cl-35 has an atomic weight of 34.97 amu, Cl-37
  has an atomic weight of 36.97 amu
• On the periodic table Cl is listed as 35.46
• (75.53 34.97) (24.47 36.97) 35.46
• 100 100

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Sec 3.3 Isotopes Atomic Masses

• Table 3.2 Page 54
• Isotopic data for
• the first 12 elements
• Some elements
• have no isotopes

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Sec 3.4 The Periodic Table

• Dmitri Mendeleev put forward the concept of
  arranging the elements by atomic weight in the
  1860s
• Periods are the horizontal rows
• Groups or columns are vertical and have similar
  chemical properties
• Example column 1 are all metals (Li, Na, K, Rb
  and all form compounds with the same ratios LiCl,
  NaCl, KCl, RbCl)

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Sec 3.4 The Periodic Table

• Main group elements numbered 1A to 8A (or 1-2
  and 13-18), the elements we are most concerned
  with
• Transition metals 3B to 8B (3-12) considered as
  one block
• Series fit inside the periodic table in the gaps

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Sec 3.4 The Periodic Table
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Sec 3.4 The Periodic Table

• Figure 3.4 Page 56. In this periodic table,
  elements 58 through 71 and 90 through 103 are
  shown in their proper positions.

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Sec 3.4 The Periodic Table

• The periodic table allows us to see patterns in
  properties of the elements
• Columns often have names Column 1A are the
  alkali metals, column 7A are the halogens, column
  8A are the noble gases

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Sec 3.4 The Periodic Table
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Sec 3.5 Metals and Nonmetals

• Metals all but 22 elements are metals.
• Metals are solids (except Mercury) and conduct
  electricity, shiny, ductile, malleable, and can
  form alloys
• Nonmetals 18 nonmetal elements
• Do not conduct electricity, include the organic
  elements (C,N,O,H,P,S)
• Metalloids 4-5 elements
• Some properties of both, in-between metals and
  non metals. Semi-conductor

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Sec 3.5 Metals and Nonmetals
Figure 3.5 Page 56

• Some familiar metals are aluminum, lead, tin, and
  zinc.

(b) Some familiar nonmetals are sulfur,
phosphorus, and bromine.
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Sec 3.5 The Periodic Table
Metals, nonmetals, and metalloids
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Sec 3.6 Electron Arrangement

• The energy of electrons in an atom is quantized,
  which means that an electron in an atom can have
  only certain allowed energies
• Ground state the electron configuration of
  lowest energy

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Sec 3.6 Electron Arrangement

• Electrons arranged into energy levels or shells
• Shells are subdivided into subshells and orbitals
• The names for the subshells come from the words
  sharp, principal, diffuse, and fundamental

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Sec 3.6 Electron Arrangement

• Each shell is able to hold more electrons
• This number expands up to a maximum of 32
• The formula is 2n2
• For shell 3, 2(3)2 18
• Figure 3.7 Page 59

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Sec 3.6 Electron Arrangement

• Orbitals have definite shapes and orientations in
  space

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Sec 3.7 Electron Configuration

• Electron configurations are governed by three
  rules
• Rule 1 orbitals fill in the order of increasing
  energy from lowest to highest

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Sec 3.7
Figure 3.10 page 61
Figure 3.11 Page 62
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Sec 3.7 Electron Configuration

• Rule 2 when there is a set of orbitals of equal
  energy, one orbital becomes half filled before
  any of them becomes completely filled
• Applies to p, d, and f orbitals
• P has 3 equal orbitals
• D has 5 equal orbitals
• F has 7 equal orbitals

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Sec 3.7 Electron Configuration

• Rule 3 each orbital can hold up to two electrons
  with spins paired
• with four electrons, the 1s and 2s orbitals are
  filled and are written 1s2 2s2
• with an additional six electrons, the three 2p
  orbitals are filled and are written either 2px2
  2py2 2pz2, or they may be written 2p6

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Sec 3.7 Electron Configuration

• Orbital box diagrams
• a box represents an orbital
• an arrow represents an electron
• a pair of arrows with heads in opposite
  directions represents a pair of electrons with
  paired spins
• Example Lithium atomic number 3

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Sec 3.7 Electron Configuration

• Example carbon (atomic number 6)

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Sec 3.7 Electron Configuration

• Example phosphorus (atomic number 15)

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Sec 3.8 Electron Configuration and Periodic Law

• Chemical Properties repeat themselves among the
  elements because electron configurations repeat
  themselves
• We find a strong correlation between electron
  configurations and chemical properties

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Sec 3.8 Electron Configuration and Periodic Law

• The arrangement of the periodic table is
  consistent with the 4 types of orbitals
• s(2), p(6), d(10), f(14)
• The last filled electron (called the
  distinguishing electron) largely determines the
  placement and hence the properties of the
  elements

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Sec 3.8
Fig 3.12 Page 67
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Sec 3.9 Classification of Elements

• Color Schemes allow us to classify the elements
  is different ways
• We have seen metals and nonmetals
• We have seen names for specific groups, and
  blocks of elements

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Sec 3.9 Classification of Elements
Chemistry at a Glance Summary Page 69
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Problems

• Assigned problems pages 70-74
• 3.4, 3.5, 3.9, 3.13, 3.14, 3.22, 3.25
• 3.31, 3.33, 3.37, 3.34, 3.53, 3.55, 3.59, 3.61
• 3.69, 3.70, 3.71, 3.72
• Practice Test Page 45-46