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Elements! Elements ►A pure element is made of many of the same atoms. ► Common elementsAluminum, Oxygen, Carbon (about 100 others) ► Elements cannot normally be broken apart into smaller substances Demitri Mendeleev- Russian chemist who developed the first periodic table in 1869. The periodic table organizes elements by common http://www.germes-online.com/direct/dbimage/50327532/Aluminum_Alloy_Pipe.jpg characteristics! http://serc.carleton.edu/images/usingdata/nasaimages/peri odic-table.gif http://www.jinshanmines.com/i/photos/Jinshan_GoldBar.jpg Atomic Model and Subatomic Particles Subatomic particles • Atomic Model has changed dramatically through history •Subatomic particles make up all atoms Protons Found in the nucleus (center of atom) The electric charge is positive (+) Weighs 1 amu (atomic mass unit) Each element has a unique number of protons (All Oxygen atoms have 8 protons; all Iron have 26) Atoms are identified by their number of protons. Neutrons Also makes up part of nucleus No electric charge Weighs 1 amu Number of neutrons in the nucleus can change (Isotopes) Electrons Found surrounding the nucleus in energy levels Negatively (–) charged particle Weighs 1/2000 amu At one time thought to be nuclear garbage. Now, the most important part of chemistry VIP of Chemistry Electron Energy Levels • Electrons have energy (they have motion) • Electrons surround nucleus in energy levels • Electrons fill the lowest energy level first which is closest to the nucleus