The Periodic Table and Periodic Law

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The Periodic Table and Periodic Law

• Chapter 6

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Section 6.1 Development of the Modern Periodic
Table

• Late 1790s- Lavoisier compiled a list of 23
  elements known at the time
• By 1870- 70 known elements
• John Newlands
• Arranged elements by increasing atomic mass
• Noticed properties repeated every eighth element
  (periodic)
• Law of Octaves

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Dmitri Mendeleev

• Russian
• 1st periodic table
• Organized elements by properties
• Arranged elements by atomic mass
• Predicted existence of several unknown elements
• Element 101 Mendeleevium (Md)

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Section 6.1 Development of the Modern Periodic
Table

• Late 1790s- Lavoisier compiled a list of 23
  elements known at the time
• By 1870- 70 known elements
• John Newlands
• Arranged elements by increasing atomic mass
• Noticed properties repeated every eighth element
  (periodic)
• Law of Octaves

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Dmitri Mendeleev

• Russian
• 1st periodic table
• Organized elements by properties
• Arranged elements by atomic mass
• Predicted existence of several unknown elements
• Element 101 Mendeleevium (Md)

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Henry Moseley

• 1913-performs experiments to determine the atomic
  number of the known elements
• Afterwards arranges the elements in the periodic
  table listing them by increasing atomic number
  instead of by mass

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Periodic Law

• When the elements are arranged in order of
  increasing atomic number, there is a periodic
  repetition of their physical and chemical
  properties

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The Modern Periodic Table

• Groups- aka families (vertical columns)
• Each group is numbered 1-8 followed by the letter
  A or B
• Representative Elements- designated with an A
  (1A-8A)
• Transition Elements- designated with a B (1B-10B)
• 18 total groups
• elements of any one group have similar physical
  and chemical properties

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• Periods- horizontal rows
• 7 total periods
• element properties change as you go across each
  row
• the pattern of properties repeats from one period
  to the next

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Classifying the Elements

• Three main classifications for the elements
• Metals
• Nonmetals
• Metalloids

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Metals

• Physical Properties
• Luster (shininess)
• Good conductors of heat and electricity
• High density (heavy for their size)
• High melting point
• Ductile (most metals can be drawn out into thin
  wires)
• Malleable (most metals can be hammered into thin
  sheets)
• Chemical Properties
• Easily lose electrons
• Corrode easily
• Alkali Metals- group 1A elements (except
  hydrogen)
• Alkaline Earth Metals- group 2A elements

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Metals Cont.

• Transition Metals
• Group B elements
• Inner Transition Metals
• Lanthanide- used as phosphors (substances that
  emit light when struck by electrons)
• Actinide

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Nonmetals

• Physical Properties
• No luster (dull appearance)
• Poor conductor of heat and electricity
• Brittle (breaks easily) or gaseous
• Not ductile
• Not malleable
• Low density
• Low melting point
• Bromine is the only nonmetal liquid at room
  temperature
• Chemical Properties
•  Tend to gain electrons

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Nonmetals Cont

• Halogens
• Group 7A
• Extremely Reactive
• Noble Gases
• Group 8A
• Extremely Unreactive

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Metalloids

• Bordering the stair-step line
• Physical Properties
• Solids
• Can be shiny or dull
• Ductile
• Malleable
• Conduct heat and electricity better than
  nonmetals but not as well as metals

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• Elements in the same group on the periodic table
  have similar chemical properties because they
  have the same valence electron configuration

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Section 6.3 Periodic Trends

• The electron cloud surrounding the nucleus is
  based on the probability and does not have a
  clearly defined edge
• Atomic size is defined by how closely an atoms
  lies to a neighboring atom

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Atomic Radii Trend

• Trends within periods
• Generally decreases as you move left-to-right
  across a period (row)
• Trends within groups
• Generally increases as you move down a group

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Ionic Radius

• An ion is an atom or a bonded group of atoms that
  has a positive or negative charge
• When atoms lose electrons and form positively
  charged ions, they always become smaller
• When atoms gain electrons and form negatively
  charged ions, they always become larger

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Lose Electrons ? Smaller ionic radii
Gain Electrons ? larger ionic radii
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Ionization Energy (I.E.)

• Ionization Energy- the energy required to remove
  an electron from a gaseous atom
• 1st Ionization Energy- removes the 1st electron
• 2nd Ionization Energy- removes the 2nd electron
  and so forth
• I.E. is an indication on how strongly an atoms
  nucleus holds onto its valence electrons

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Octet Rule- atoms tend to gain, lose or share
electrons in order to acquire a full set of eight
valence electrons
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• Octet Rule- atoms tend to gain, lose or share
  electrons in order to acquire a full set of eight
  valence electrons
• Hydrogen and Helium are exceptions (theyll be
  happy with 2 V.E.)
• Determines the types of ions likely to form
• Elements on the right side tend to gain electrons
• Elements on the left side tend to lose electrons

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Electronegativity

• Indicates the relative ability of its atoms to
  attract electrons in a chemical bond
• Noble gases form very few compounds so they are
  left out
• In a chemical bond, the atom with the greater
  electronegativity more strongly attracts the
  bonds electrons

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In Summary
Atomic radius decreases Ionization energy
increases Electronegativity increases
Atomic radius increases Ionization energy
decreases Electronegativity decreases
1A
0
2A
3A
4A
6A
7A
5A
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Homework

• Page 174-175
• 29-38
• 40-45
• 47-76