Group VII of the PT

The elements of group VII are called halogenes. They have 7 valency electrons (of course in the outer shell) and they like to have one more, just to have 8 in total. With 8 electrons in the outer level, the atom (ion) becomes a lot more stable.

Below some data about group VII
halogeen symbol atom number atom mass density
in g/cm3		 melting point
in K		 boiling point
in K		 color
fluorine
F2
9
19,0
1,11
53
85
yellow
chlorine
Cl2
17
35,5
1,56
172
239
Yellow green(g)
bromine
Br2
35
79,9
3,12
266
331
red brown(l)
iodine
I2
53
126,9
4,94
387
456
black(s)

Astatium (also a halogene) is radioactive

The elements of group VII can be characterised with ns2 np5, n≥2