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

The halogens are in group 7

4. Iodine * dark purple crystals

* starch tester and mild disinfectant

HIGHER TIER

eg Na+ , K+

HIGHER TIER

HIGHER TIER

HIGHER TIER

Helium

Neon

Argon

Krypton

Xenon

Radon

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!

l m

o

a o e

s

l i

c n

f

b

K

Ca

2,6

2,8,7

O - -

Ca ++

2,8,8 +

2,8 -

2,8,8 - -