Pure substances that cannot be separated into different substances by ordinary processes Are the building blocks of matter 112 elements known today Examples: carbon gold calcium LecturePLUS Timberlake8
Use 1 or 2 letter abbreviations Capitalize the first letter only Examples: C carbon Cocobalt N nitrogenCacalcium F fluorine Br bromine O oxygen Mg magnesium LecturePLUS Timberlake9
Atomic Number Atomic Number –Equal to # protons = # electrons –Periodic Table is arranged by this number Symbol Symbol –“Shorthand” for the element – Note 2 nd letter is always lowercase Atomic Mass Number Atomic Mass Number –Total AVERAGE mass of Protons + Neutrons + Electrons 17 Cl 35. 5
Electrons are arranged in “Shells” around nucleus in predictable locations Fill “seats” closest to nucleus first (concert – best seats) “Seats” available ◦ Shell #12 electrons ◦ Shell #28 electrons ◦ Shell #38 electrons ◦ Shell #4 18 electrons ◦ Shell #5 32 electrons ◦ Shell #650 electrons Ex. Carbon has 6 total electrons so… Two electrons on first energy level Four electrons on second energy level Question: Could we fit more electrons on the second energy level if there were more electrons in carbon??
17 Cl 35. 5 Total Mass of Nucleus 36 - 17 = 18 neutrons Element Name Chlorine Total # of protons and electrons (in a neutral atom) 17 protons in nucleus 17 electrons orbiting nucleus Notice: electrons follow energy level rules from previous slide. (Round Atomic Mass)
Vertical columns on the periodic table Similar physical properties Similar chemical properties LecturePLUS Timberlake22