The Periodic Table Glencoe Chapter 19 3 Page

The Periodic Table Glencoe: Chapter 19 -3 Page 588 -596

Organizing the Elements • Late 1800’s (1871), Dmitri Mendeleev • Russian chemist • Created 1 st 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

Table Parts • Groups – vertical columns (up-anddown) 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).