What is the periodic table? Rows and columns periodic- a regular repeating pattern groups or families- columns (vertical) The periodic table periodic table- arrangement of elements so that period- rows (horizontal) their physical and chemical properties follow a everything in a group shows similar properties regular repeating pattern Why properties repeat? Dmitri Mendeleev physical and chemical properties are mainly Element #101 was named in his honor affected by valence electrons. History of the Periodic Table first to come up with a periodic table Everything in the same column will always have ~1870 there were 63 elements known to man, he the same number of valence electrons. organized the elements in order of their atomic mass, he saw a pattern form with the # of elements that can be bonded to that element. More Mendeleev Medeleev’s Table The pattern has to do with the valence electrons It may not sound like much, but… He arranged his table so that columns of elements He predicted what undiscovered elements would be with the same valence electrons formed, he left like giving specifics!!! spaces in his table where it appeared an element And he was Right! wasn’t discovered yet This is the basis for acceptance of scientific work. Can He even predicted the properties of these elements you make predictions that can be tested? by looking at the other elements in the family and He did, and he was correct. Which tells us a bunch of period of that element information about the world! All holes have been filled in (three while he was still alive) and his predictions came out pretty close 1 1871 Discovery Dmitri Mendeleev Property Ekaaluminum Gallium 1882 Discovery (Mendeleev’s Property Ekasilicon Germanium prediction) atomic mass 72 72.61 atomic mass 68 69.72 density (g/cm³) 5.5 5.35 density (g/cm³) 6.0 5.904 melting point (°C) high 947 color grey grey melting point Low 29.78 oxide type refractory dioxide refractory dioxide (°C) oxide density (g/cm³) 4.7 4.7 oxide's formula Ea2O3 (density - 5.5 g Ga2O3 (density - 5.88 g cm-3) cm-3) oxide activity feebly basic feebly basic (soluble in both alkalis and (soluble in both alkalis and acids) chloride boiling point under 100°C 86°C (GeCl4) acids) chloride density (g/cm³) 1.9 1.9 chloride's Ea2Cl6 (volatile) Ga2Cl6 (volatile) formula Henry Moseley Problem with Mendeleev’s table Henry Moseley ~1910 Mendeleev arranged his table by atomic mass Discovered atomic number (# of protons of an atom) a few elements appeared to be slightly out of place, Mendeleev put them in the right place and He rearranged the periodic table by this number guessed that their atomic masses were and it fell into perfect order incorrectly measured -Mendeleev’s table worked because as the number of protons increase the atomic mass Actually, he was arranging them by the wrong should increase, however if there are fewer number. neutrons it could decrease Names of different sections Periodic Law Main group elements- groups 1, 2 , 13-18 Alkali Metals- first column (Group 1) excluding H The periodic law states that physical and Alkaline Earth Metals-Group 2 chemical properties of the elements are periodic Parts of the Periodic Table Transition Metals- groups 3-12 functions of their atomic numbers Halogens- Group 17 In other words, when the elements are arranged Noble Gases- Group 18 by their atomic numbers you should see chemical Lanthanide Series Top row on the bottom two and physical properties repeating themselves Actinide Series bottom row of the bottom two Lanthanide and Actinides fit into the table above 2 Families Have similar properties Periodic Table Key Transition Metals Noble Gases are extremely inactive or inert Always pay attention to the key of a periodic table (doesn’t like to react w/ anything) because everyone looks slightly different That is because they have a full valence shell 3 things will pretty much always be in a square (the state everything wants to be in) (some tables have much more) Noble Gases Alkali Metals Halogens Alkaline Alkaline Earth Metals Halogens are extremely reactive 1- atomic number Alkali metals are extremely reactive 2- chemical symbol 13 Lanthanide Series Transition metals are slightly reactive 3- atomic mass Al Actinide Series 26.981539 Metals vs. Nonmetals Metals Use the steps on the periodic table to determine Physical properties- luster, conductive, malleable, ductile, what type an element is. high density, high melting point All except Hg are solids at room temperature Left of the steps are metals (Except H) Chemical properties- most metal will react with O2 or H2O Right of the steps are nonmetals to form an oxide (metal + Oxygen), This is rusting or Elements on the steps are metalloids or tarnishing. semiconductors (except Al-it is a metal) When this compound rubs off the surface of the elemental metal it is called corrosion Metals give up e- to get to a full valence shell Hydrogen Nonmetals Metalloids (semiconductors) Hydrogen fits into its own group and is not an Physical properties- dull, don’t conduct, brittle, can be shiny or dull, conduct ok, ductile and alkali metal or even a metal low density, low melting points malleable or brittle This is because it is only 1 proton and 1 electron Can be solid, liquid or gas at room temperature These elements have become really important (no neutrons) depending on the element because of the computer revolution - Computer chips are made out of semiconductors although under the extreme pressure on Jupiter it Nonmetals take e to get a full valence shell (normally Si) may act like a metal by position Al is a metalloid, but its properties make it a light metal 3.