Transcript Chapter 18
8th Grade Science-Periodic Table Properties of the Periodic Table The Periodic Table • Dimitri Mendeleevarranged all the elements known in order of increasing atomic masses and discovered a pattern • Today’s Periodic Table— elements are arranged by increasing atomic number and by changes in physical and chemical properties • Mendeleev-left blank spaces to keep elements in line according to chemical properties • He predicted the existence of two elements not yet discovered Groups • The vertical columns in the periodic tablealso called families • Elements in groups have similar properties • Periodic Table—pg. 128 and 129 in textbook *Elements in the same group have the same number of valence electrons *This means these elements will all bond similarly Periods/Rows • Horizontal groups across the periodic table • Each row ends with an element with a full outer valence (8 electrons) • Periods increase by one proton and one electron going L to R • Many other properties of elements increase either left to right or right to left across the periodic table as well. • Ex: electronegativity, atomic radii, etc. Metals • Metals are on the lefthand side of the periodic table • Most are shiny, ductile, malleable and are good conductors • Ductile—drawn into wire • Malleable-can be hammered into sheets Non-metals • Non-metals are on the right side of the periodic table • Most are gases, brittle, are poor conductors, and are solids at room temperature Metalloids • Metalloids-run along the middle zig-zag line • Metalloids have some of the properties of both metals and non-metals Metalloids • Are considered semiconductors—can conduct electricity better than nonmetals, but not as well as metals • *Review pg. 135 of book Groups of the Periodic Table • Group 1—Alkali Metals • All have 1 valence electron and are highly reactive • Group 2—Alkaline Earth Metals • All have 2 valence electrons and are reactive, but not quite as reactive as Group 1 • Groups 3-12 *Called the “Transition Elements” because they are in transition between Groups 1 and 2 and Groups 13-18 *They have no specific number of valence electrons per group Group 13 elements-Boron Group • All have 3 valence electrons • Boron-metalloid-common in some household products-borax, boric acid • Aluminum-most abundant metal in Earth’s crust • (cans, foil, pans, siding) Group 14 elements-Carbon Group • Carbon-silicon, nonmetal, silicon and germanium are metalloids, and tin and lead are metals • Carbon occurs as an element in coal, oil, natural gas, foods • All Group 14 elements have 4 valence electrons Group 15 Elements-Nitrogen Group • All have 5 valence electrons • Tend to share electrons when bonding • Ex: ammonia, fertilizer, nitrates • Phosphorus-water softeners, fertilizers, match heads, china • Antimony and Bismuth-low melting points/mixed w/other metals Group 16 –Oxygen Group • All have 6 valence electrons • Exists in air as a diatomic molecule • Ozone-protects us from sun’s radiation • Sulfur-nonmetal, exists in different forms, used as pigment in paint Group 17 Elements-Halogens • All have 7 valence electrons, so very reactive • Form compounds that have many usestoothpaste, disinfectants, etc. • Form salts when they bond with other elements Group 18 Elements-Noble Gases • Have 8 valence electrons • Satisfy the “octet rule” • Are very stable and do not bond with other atoms in nature • *used for neon signs, lighting, balloons, etc. Lanthanide and Actinide Series • Located at bottom of periodic table • Separated from rest of periodic table to keep other elements in order • Most are man-made elements Synthetic Elements • Scientists break apart elements in order to make new SYNTHETIC elements • Synthetic elements on the periodic table are those with an atomic # greater than 92 • CHNOPS-Carbon, Hydrogen, Nitrogen, Oxygen, Phosphorus, Sulfur • These are the most abundant elements in living organisms Diatomic Elements • These elements exist naturally as diatomic elements (2 atoms bonded together) • Hydrogen Iodine • Nitrogen Chlorine • Fluorine Bromine • Oxygen • Acronym: Have No Fear of Ice Cold Beverages Periodic Table websites: • • • • www.chemicool.com www.Ptable.com www.periodictable.com www.webelement.com