The halogens are in group 7
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Transcript of The halogens are in group 7
The halogens are in group 7
1. Fluorine gas *pale yellow
2. Chlorine gas * yellow/ green
3. Dark brown liquid and vapour
Added to toothpaste to strengthen teeth and bones
The halogens are in group 7
1. Fluorine gas *pale yellow
3. Dark brown liquid and vapour
* Explodes with hydrogen forming HCl which dissolves in water to make hydrochloric acid
*used for making PVC , *preparing circuit boards * killing germs
2. Chlorine gas * yellow/ green
The halogens are in group 7
3. Bromine Dark brown liquid and vapour
Silver bromide isused in photography
IonsAn ion is formed when an atom gains or loses electrons and becomes charged:
If we “take away” the electron we’re left with just a positive charge:
This is called an ion (in this case, a positive hydrogen ion)
+-
+
The electron is negatively charged
The proton is positively charged
+
Na
Na
+
Cl
Cl
-
An atom of Sodium 2.8.1.
An ion of Sodium
An atom of Chlorine 2.8.7.
An ion of Chlorine
A salt crystal of sodium chloride
is formed
Diagrams show outermost shell of electrons only
Outermost shell loses one electron
Outermost shell gains one electron
2.8 2.8.8
Na
Na
+
Cl
Cl
-
An ion of Sodium 2.8
An ion of Chlorine 2.8.8
A salt crystal of sodium chloride
is formed
The attractive force between a positive and
negative ion forms a special bond called an “ionic Bond”
This is why salt crystals have a very high
melting point!