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The History of the Periodic Table:

Early 1800's:
-Elements were arranged in order of atomic mass
-Scientists had no idea about atomic structure

Alexander NEWLAND-1864:
-Noticed every 8th element had similar properties
-Arranged tables in rows of 7 Newland Octaves
-No gaps left for undiscovered elements
-Metals and non-metals…

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The Modern Periodic Table is Based on:
-Electronic structure Making it easier to predict properties
-Shells Corresponding to energy levels
-The further away an electron is from the nucleus the less of an attraction it has to it
-Lots of inner electrons causes SHEILDING=Electrons getting in…

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Group 7:
-Halogens (non-metals with coloured vapours)
-7 outer electrons
-Molecules consists of PAIRS OF ATOMS
-As you go down elements get LESS REACTIVE and have a HIGHER BOILING AND MELTING POINTS

Group 7
Other Properties Colour

Fluorine Very reactive YELLOW GAS

Chlorine Fairly reactive GREEN GAS

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-Form IONICS BONDS with METALS producing 1¯ ions called HALIDES (NaCl)
-More reactive halogens DISPLACE less reactive ones from an AQEOUS SOLUTION of its salt

Transition Metals: In between Group 2 and 3

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-Good conductors of heat and electricity
-Dense, strong and shiny
-Don't react vigorously with water or oxygen (unlike Group 1 metals)
-Denser, stronger and harder than Group 1 metals
-Have higher melting points than Group 1 metals
-Often have more than 1 ion different number of ions form different colours…

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-Caused by dissolved Ca² and Mg² ions
- Dissolved calcium and magnesium ions react with soap to make scum
-Need more soap to produce good lather
-When heated/boiled it forms scale on the inside of the appliance reducing its efficiency so things like heating pipes or boilers may need to…

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Both Types of Hardness can be Removed by:
Adding Washing Soda:
-Added carbonate ions react with Ca² and Mg² ions to form an insoluble precipitate of Calcium carbonate and Magnesium carbonate Getting rid
of the ² ions

Ion Exchange Columns:
-Columns contain sodium/hydrogen ions which are exchanged for the calcium…


Subash Poudyal


Absolutely fantastic! thanks a lot :)

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