Glencoe: Chapter 19-3 Page 588-596 The Periodic Table Glencoe: Chapter 19-3 Page 588-596
Organizing the Elements Late 1800’s (1871), Dmitri Mendeleev Russian chemist Created 1st periodic table by placing all known elements (at that time ~ 60 elements) in order by increasing atomic mass (number of neutrons + number of protons)
Organizing the Elements Discovered a pattern Heavier elements repeated the chemical properties of lighter elements Periodic properties – a repeating pattern of chemical properties
Early Periodic Tables This table show gaps for unknown elements
Organizing the Elements Mendeleev left blank spaces in his arrangement in order to attempt to align elements with similar properties Predicted chemical properties and atomic masses of elements not yet known, for which he had left blank spaces to be filled in when the elements were discovered.
Organizing the Elements Mendeleev’s predictions were correct When found, the missing elements in Mendeleev’s table did possess properties and masses very close to Mendeleev’s predictions Known as the “Father of the Periodic Table”
Improving the Periodic Table As more elements were discovered, Mendeleev’s table needed some changes to deal with inconsistencies 1913 – Henry Moseley (English scientist) – arranged the elements by increasing atomic number (number of protons)
Improving the Periodic Table This new arrangement corrected some inconsistencies in the periodic properties The modern / current periodic table is arranged by increasing atomic number, from Moseley.
Periodic Table
Periodic Table
Table Parts Groups – vertical columns (up-and-down) of elements on the periodic table All elements in a group share / possess similar chemical properties, and electron arrangements Also called families of elements There are 18 groups / families of elements
Table Parts Periods – horizontal rows (side-to-side) of elements on the periodic table There are 7 periods Elements increase atomic number from left to right across a period
Regions of the Table / Classifications There are four general regions on the periodic table. 1. Metals 2. Metalloids 3. Non-metals 4. Noble gases
Table Regions
Synthetic elements / Man-made elements Scientists are continually attempting to make new, bigger (higher atomic number), and heavier elements They smash particles and atoms together to see what “sticks”
Synthetic elements / Man-made elements Most break down on their own radioactive Radioactive elements / isotopes of elements are unstable and break apart on their own into parts that are more stable
Elements in the Universe Through study it appears that the universe is made of all the same stuff Hydrogen (H) and Helium (He) are the most abundant elements in the universe.
Elements in the Universe Heavier elements are constantly being formed in stars by nuclear fusion (joining of smaller nuclei into larger nuclei).