The Periodic Table: A Comprehensive Overview, Slides of Chemistry

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The Periodic Table

The Periodic Table

• Discovered by Dmitri Mendeleev in 1869 as a display of the chemical elements in order of atomic mass
• The arrangement of the elements displays “periodic trends” of chemical elements
• In 1911, Henry Moseley recognized that if the elements were organized based on nuclear charge (# of protons), the patterns fit better than if organized by atomic mass.
• This led to the Periodic Law and since 1911 the periodic table has undergone changes due to new discoveries

Periodic Elements

C

Carbon

1s^2 2s^2 2p^2

Atomic Number

Symbol

Name Average atomic mass(also called Molar Mass) Electron Configuration

Groups and Periods

• Periods go left to right
• Groups go up and down

Atomic Number

• This is the number of Protons in an element. The atomic number for atoms of the same element will always be the same. This is the signature for identifying elements.

Atomic Symbol

• This is the accepted abbreviation for the element. Usually written in the biggest font on the periodic table.