History of the Periodic Table - Copley

History of the Periodic Table - Copley

The periodic table What is the periodic table? periodic- a regular repeating pattern periodic table- arrangement of elements so that their physical and chemical properties follow a regular repeating pattern Rows and columns

groups or families- columns (vertical) period- rows (horizontal) everything in a group shows similar properties Why properties repeat? physical and chemical properties are mainly affected by valence electrons.

Everything in the same column will always have the same number of valence electrons. History of the Periodic Table Dmitri Mendeleev Element #101 was named in his honor first to come up with a periodic table

~1870 there were 63 elements known to man, he 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. The More Mendeleev pattern has to do with the valence electrons He arranged his table so that columns of elements

with the same valence electrons formed, he left spaces in his table where it appeared an element wasnt discovered yet He even predicted the properties of these elements by looking at the other elements in the family and period of that element Medeleevs Table It may not sound like much, but

He predicted what undiscovered elements would be like giving specifics!!! And he was Right! Neither Nostradamus nor any psychic hotline can claim that! All holes have been filled in (three while he was still

alive) and his predictions came out pretty close 1871 Discovery Property Ekaaluminum (Mendeleevs prediction) atomic mass 68 density (g/cm) 6.0

melting point Low (C) oxide's formula Ea2O3 (density - 5.5 g cm-3) chloride's formula Gallium 69.72 5.904

29.78 Ga2O3 (density - 5.88 g cm-3) (soluble in both alkalis and acids) (soluble in both alkalis and acids) Ea2Cl6 (volatile)

Ga2Cl6 (volatile) 1882 Discovery Property atomic mass density (g/cm) melting point (C) color oxide type oxide density (g/cm) oxide activity

chloride boiling point Ekasilicon 72 5.5 high grey refractory dioxide 4.7 feebly basic under 100C

Germanium 72.61 5.35 947 grey refractory dioxide 4.7 feebly basic 86C (GeCl4)

chloride density (g/cm) 1.9 1.9 Dmitri Mendeleev Problem with Mendeleevs table Mendeleev

arranged his table by atomic mass a few elements appeared to be slightly out of place, Mendeleev put them in the right place and guessed that their atomic masses were incorrectly measured Actually, he was arranging them by the wrong number. Henry Moseley ~1910 Discovered

atomic number (# of protons of an atom) He rearranged the periodic table by this number and it fell into perfect order -Mendeleevs table worked because as the number of protons increase the atomic mass should increase, however if there are fewer neutrons it could decrease

Henry Moseley Periodic Law The periodic law states that physical and chemical properties of the elements are periodic functions of their atomic numbers In other words, when the elements are arranged by their atomic numbers you should see chemical and physical properties repeating themselves

Parts of the Periodic Table Names of different sections Main group elements- groups 1, 2 , 13-18 Alkali Metals- first column (Group 1) excluding H Alkaline Earth Metals-Group 2 Transition Metals- groups 3-12

Halogens- Group 17 Noble Gases- Group 18 Lanthanide Series Top row on the bottom two Actinide Series bottom row of the bottom two Lanthanide and Actinides fit into the table above Lanthanide Series Actinide Series Noble Gases

Halogens Alkaline Earth Metals Alkali Metals Transition Metals Families Have similar properties Noble

Gases are extremely inactive or inert (doesnt like to react w/ anything) That is because they have a full valence shell (the state everything wants to be in) Halogens are extremely reactive Alkali metals are extremely reactive Transition metals are slightly reactive Periodic Table Key Always

pay attention to the key of a periodic table because everyone looks slightly different 3 things will pretty much always be in a square (some tables have much more) 1atomic number 2chemical symbol 13 3atomic mass Al 26.981539

Metals vs. Nonmetals Use the steps on the periodic table to determine what type an element is. Left of the steps are metals (Except H) Right of the steps are nonmetals Elements on the steps are metalloids or semiconductors (except Al-it is a metal)

Metals Physical properties- luster, conductive, malleable, ductile, high density, high melting point All except Hg are solids at room temperature Chemical properties- most metal will react with O or 2 H2O to form an oxide (metal + Oxygen), This is rusting or tarnishing. 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 Hydrogen fits into its own group and is not an alkali metal or even a metal This is because it is only 1 proton and 1 electron (no neutrons) although under the extreme pressure on Jupiter

it may act like a metal Nonmetals Physical properties- dull, dont conduct, brittle, low density, low melting points Can be solid, liquid or gas at room temperature depending on the element Nonmetals take e- to get a full valence shell

Metalloids (semiconductors) can be shiny or dull, conduct ok, ductile and malleable or brittle These elements have become really important because of the computer revolution Computer chips are made out of semiconductors (normally Si) by position Al is a metalloid, but its properties

make it a light metal

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