Elements & Their Properties John Newlands 1837-1898 Dmitri Mendeleev.
THE PERIODIC TABLE Chapter 19 Section 3. Organizing the Elements In the late 1800s, Dmitri Mendeleev...
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Transcript of THE PERIODIC TABLE Chapter 19 Section 3. Organizing the Elements In the late 1800s, Dmitri Mendeleev...
THE PERIODIC TABLEChapter 19
Section 3
Organizing the Elements• In the late 1800s, Dmitri Mendeleev searched for a way to
organize the elements• His first arrangement was done by increasing atomic
masses• Found a pattern
• Chemical properties in lighter elements were repeating in heavier elements
• The pattern was Periodic
• The arrangement is now known as the periodic table• Mendeleev’s table was so well constructed that he was
able to predict the location of elements that had not yet been discovered.
Improving the Periodic Table• Mendeleev’s table was arranged by atomic mass• But there were some spots were atomic mass placement
and atomic properties didn’t make sense• Cobalt and Nickel
• In 1913, Henry Moseley proposed a table arranged by increasing atomic number• This change corrected the problems found in Mendeleev’s table• Moseley’s arrangement is the one used in the modern table of
elements
The Atom and the Periodic Table• The vertical columns of the periodic table are known as
groups• The atoms of elements found in the same family have
similar properties• This is due to the number of electrons in the outer energy
level
Electron Cloud Structure• Electrons in the electron cloud have different energies• The differences are modeled by placing them in energy
levels.• Low energy Close to the nucleus• High energy Further away from the nucleus• Labeled from 1 to 7• Energy level 1 can hold up to two electrons• Energy level 2 can hold up to 8 electron• Energy level 3 can hold up to 18 electrons• A complete and stable outer energy level will have 8 electrons• Sooo…elements in the same column have the same number of
electrons in the outer energy level
Rows on the Table• As you go across the table, an electron is added to the
outer shell and one proton is added to the nucleus• The row tells you with energy level the outer most
electrons are located in• The rows are called periods
Electron Dot Diagrams• Electron dot diagrams were introduced by G.N Lewis • They are a short hand way of showing how many
electrons are in the outer energy level• They are also used to show how atoms combine to form
compounds• Electron dot diagrams will be the same for all elements in
a column
Regions on the Periodic Table