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) ol Gases Noble laiMetals Alkali Halogens

Alkaline Earth MetalsEarth Alkaline 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

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