Elements Elements A pure element is made of
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Elements!
Elements ►A pure element is made of many of the same atoms. ► Common elements. Aluminum, 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_Gold. Bar. jpg
Atomic Model and Subatomic Particles • Atomic Model has changed dramatically through history Subatomic particles • Subatomic particles make up all atoms
Protons Found in the nucleus (center of atom) n The electric charge is positive (+) n Weighs 1 amu (atomic mass unit) n Each element has a unique number of protons (All Oxygen atoms have 8 protons; all Iron have 26) n Atoms are identified by their number of protons.
Neutrons n n Also makes up part of nucleus No electric charge Weighs 1 amu Number of neutrons in the nucleus can change (Isotopes)
Electrons n n 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 n 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
