The Periodic Table : The Periodic Table Part One
The Basics : The Basics What does periodic mean?
Having or marked by repeated cycles
What things in our everyday life do we notice as cyclic or periodic?
What are some of the patterns you notice on the periodic table?
There are many important people who played a key role in organizing the elements in such an intricate fashion…
Antoine Lavoisier (1790’s) : Antoine Lavoisier (1790’s) Compiled a list of known elements at the time (23)
What elements do you think were included here?
Gold, silver, oxygen, carbon
The 1800’s brought about big changes…
Slide 4 : What are some big things that may have affected the knowledge of chemistry?
Electricity
Development of the spectrometer
Industrial revolution (mid-1800’s)
Lead to many chemical industries…soaps, dyes, fertilizers
But not all good things came from the revolution
Chemical pollution now an issue
70 known elements by the 1870
In addition to new elements… : In addition to new elements… New scientific data that provided insight into the properties of compounds and elements
A tool for organization became necessary
Big step: 1860
Scientists agreed on a method for accurately determining the atomic masses of the elements (finally!)
What would be the problem with not having a universal way to measure the mass of elements?
Now the search for relationships between mass and elements was on…
John Newlands (1864) : John Newlands (1864) English chemist
Proposed organization scheme
Noticed elements were arranged by increasing atomic mass
Also, their properties repeated every eigth element
1st and 8th
2nd and 9th
What do were call this repeating pattern?
Newlands called it: The Law of Octaves
Octave is a group of musical notes that repeats every eighth tone
Slide 7 : Newlands organized the first 14 known elements
Elements with similar properties were in the same row
How does this compare with our current periodic table
Slide 8 : The Law of octaves was not readily accepted b/c it did not work with all elements
Newlands law was also criticized b/c the use of the word octave was considered very “unscientific”
The important thing was that Newland recognized that properties of elements were repeated
Lothar Meyer (1869) : Lothar Meyer (1869) German chemist
Demonstrated connection between atomic mass and elemental properties
Did not receive as much credit as Dmitri Mendeleev because he did not publish his organization scheme first
Dmitri Mendeleev (1869) : Dmitri Mendeleev (1869) Russian chemist demonstrated connection between atomic mass and elemental properties
Noticed (like Newlands) that when elements were put in order of atomic mass there was a periodic repetition of their elemental properties
Arranged elements in order of increasing atomic mass into columns with similar properties
This was the first periodic table
Slide 11 :
Slide 12 :
Slide 13 : Mendeleev’s table was widely accepted because it predicted the existence and properties of undiscovered elements
Blank spaces on the table
Predicted properties of yet to be discovered elements such as scandium, gallium, and germanium
But there were problems… : But there were problems… New elements discovered and atomic masses were more accurately determined
Elements in Mendeleev’s table not in correct order
Arranging elements by mass now put groups of elements together with different properties
Henry Moseley (1913) : Henry Moseley (1913) English Chemist
Figured out the problem with Medeleev’s Table
What did Moseley Discover before?
Atoms of each element contain unique number of protons in their nuclei
He arranged elements in order of increasing atomic number and not increasing atomic mass
Problem Solved! : Problem Solved! Moseley’s arrangement solved the problems with Mendeleev’s table
His arrangement resulted in clear periodic patterns of properties
Lead to Periodic Law:
Statement that there is a periodic repetition of chemical and physical properties of the elements when they are arranged in increasing atomic number
Problem-solving lab p 155 : Problem-solving lab p 155
Modern Periodic Table : Modern Periodic Table