chapter 5 the periodic law. chapter 5: the periodic law 5.1 history of the periodic table 5.2...
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Chapter 5Chapter 5The Periodic LawThe Periodic Law
Chapter 5: The Periodic Law
5.1 History of the Periodic Table5.2 Electron Configuration and the Periodic
Table5.3 Electron Configuration and Periodic
Properties
Modern Russian TableModern Russian Table
Chinese Periodic TableChinese Periodic Table
Orbital Filling TableOrbital Filling Table
Periodic Table with Group NamesPeriodic Table with Group Names
Chapter 5Chapter 5The Periodic LawThe Periodic Law
5.1 History of the Periodic Table
Predecessors to the Modern Periodic Predecessors to the Modern Periodic TableTable
• Dobereiner’s TriadsJ.W. Dobereiner classified some elements into groups of three, which he called triads.
• similar chemical propertiessimilar chemical properties• physical properties varied in an orderly physical properties varied in an orderly
way according to their atomic masses.way according to their atomic masses.
Searching For an Organizing Principle
– Chlorine, bromine, and iodine have very similar chemical properties.
• 1750 only 17 elements known• 1789 Antoine Lavoisier grouped
known elements (4 groups)– Metals– Non-metals– Gases– Earths
• Next 80 yrs scientists looked for better way to classify known elements
Antoine LavoisierAntoine Lavoisier
Stanislao CannizzaroStanislao Cannizzaro(1826-1910)
• Italian chemist• Determined a method
for accurately measuring the relative masses of atoms
• His method allowed chemists to search for a relationship between atomic mass and other properties of elements
Mendeleev’s Periodic TableMendeleev’s Periodic Table• 1869….Dmitri Mendeleev (Russian
teacher and chemist) organized known elements while playing solitaire (about 70 known)– Made deck of cards with
elements– Listed name, mass and
properties• Paid attention to how elements
reacted in chemical reactionsDmitri MendeleevDmitri Mendeleev
Mendeleev’s Periodic TableMendeleev’s Periodic Table
Dmitri MendeleevDmitri Mendeleev
Predecessors to the Modern Periodic Predecessors to the Modern Periodic TableTable
• Mendeleev’s Periodic TableDmitri Mendeleev realized that the chemical and physical properties of the elements repeated in an repeated in an orderly wayorderly way when he organized the elements according to increasing atomic massincreasing atomic mass.
• In 1869, Mendeleev published a table of the elements organized by increasing atomic mass.
• Mendeleev was a Russian scientist and is often referred to as the “FatherFather” of the Periodic Table.
• PeriodicityPeriodicity is the tendency to recur at regular intervals.
Mendeleev’s TableMendeleev’s Table"The chemical properties of the elements are a periodic
function of their atomic weights"
He called this element eka-Aluminum.
Later it was renamed Gallium after its
discovery in 1875
Mendeleev's Periodic TableMendeleev's Periodic Table
• Mendeleev made some exceptions to place elements in rows with similar properties (telluriumtellurium & iodine'siodine's places were switched)
• Missing ElementsMissing Elements: gaps existed in Mendeleev’s table• Mendeleev predicted the properties of the “yet to be
discovered” elements(scandium, germanium and gallium)
VerticalVertical column
s in atomic weight order
HorizontalHorizontal rows have similar chemical properties
Problems with Mendeleev’s TableProblems with Mendeleev’s Table
Moseley helped to clarify some of the problems…
Why didn't some Why didn't some elements fit in order of elements fit in order of
increasing atomic increasing atomic mass?mass?
Why did elements exhibit Why did elements exhibit periodic behavior?periodic behavior?
Henry Moseley 1887-1915Henry Moseley 1887-1915• English physicist who determined
the number of positive charges in the nucleus (protons) by measuring the wavelength of the x-rays given off by certain metals in 1913.
• He was killed by a sniper in Turkey in August 1915 during WWI. Many people think that Britain lost a future Nobel Prize winner. This is because Nobel Prizes, the most prestigious awards for scientific achievement are awarded only to living people.
Moseley and the Periodic Table Moseley and the Periodic Table • Protons and Atomic Number:
X-ray experiments revealed a way to determine the number of protons in the nucleus of an atom
The periodic table was found to be in atomic The periodic table was found to be in atomic number order, not atomic mass order!!!number order, not atomic mass order!!!
• This explained tellurium-iodine anomaly
• ***Moseley was killed in battle in 1915, during WWI. He was 28 years old
The Periodic LawThe Periodic Law The physical and chemical properties of the
elements are periodic functions of their atomic numbers
Discovery of the Noble Gases
1868 1894 1895 1898 1900
Helium discovered as a component of the sun, based on the emission spectrum of sunlight
Freidrich Dorn
discovers radon
William Ramsay discovers
argonRamsay
finds helium on Earth
Ramsay discovers
krypton and xenon
Sir William Ramsay
• The LanthanidesThe LanthanidesEarly 1900's the elements from cerium (#58) to lutetium (#71) are separated and identified. Also known as the rare earth elements, less than 0.01% naturally occurring.
• The ActinidesThe ActinidesDiscovery (or synthesis) of thorium, # 90 to lawrencium #103
• Both groups pulled out of the table for space reasons. • Periodicity:
Elements with similar properties are found at regular intervals within the "periodic" table
The Periodic Law• The periodic law: When elements are
arranged in order of increasing atomic number, there is a periodic repetition of their physical and chemical properties.
– The properties of the elements within a period change as you move across a period from left to right.
– The pattern of properties within a period repeats as you move from one period to the next.
In the modern periodic table, elements are arranged in order of increasing atomic number.
Squares in the Periodic Table•The periodic table displays the symbols and names of the elements, along with information about the structure of their atoms.
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