Group 17 / VIIA; Halogens

Halogens are aggressive and dangerous gases or solids (iodine, I) that react with almost anything. Fluorine (F) is probably the element that forms the most compounds - even with some noble gases.
Fluorine is of immense importance in technology: without hydrofluoric acid (HF) there would be no semiconductor industry. Even exotic compounds like tungsten-hexa- fluoride (WF6) are of importance.
Fluoride or fluorspar (CaF2) is the naturally occurring mineral for making fluorine but it is also used as "flux" in smelting metals.
Chlorine (Cl) is not only part of rock salt (NaCl) but one of the most important basic ingredients of chemistry, e.g. as hydrofluoric acid (HCl).
Bromine (Br) and iodine (I) are know from medical applications but are not all that important anymore, Not so long ago, photography used "film" and for that you needed light sensitive chemicals containing those elements
Astate is radioactive, does not occur in nature and thus of no interest.
Table of Basic Data
 
Name
(German) 		Fluorine
Fluor		 Chlorine
Chlor		 Bromine
Brom 		Iodine
Iod Jod 		Astatine
Astat
Atomic number 9 17 35 53 85
Atomic mass [u] 19 35,45 79,90 126,90 209,99
Melting point [K] 53,53 172,17 265,9 386,65 575
Melting point [oC] -219,5 -100,8 -7 113,6 302
Melting point [oF]          
Boiling point [K] 85,01 238,55 332,93 457,55 610
Density [g/cm3] 1,58·10-3 2,95·10-3 3,14 4,94 ?
Ionization energy [eV] 17,42 12,97 11,81 10,45 9,5
Electronegativitiy 4,1
(largest)		 2,8 2,7 2,2 2,0
Atomic radius [pm] 70,9 99,4 114,5 133,1 ?
Ionic radius [pm] 133 181 196 220 227
Oxidation numbers -1 -1; 7,5,3,1 -1; 7,5,3,1 -1; 7,5,3,1 -1; 7,5,3,1
Lattice typ
Transformation temp. [oC]		 ? tet op op ?
Lattice constant [Å]
(a or c)		 - - - - -
Young's - Modul us [GPa] - - - - -
Therm. expansion coefficient a
[10-6K-1]		 - - - - -
 
In case of doubt all numbers are for room temperatures
fcc = face centered cubic; lattice const. = a
bcc = body centered cubic
sc = simple cubic
hp = simple hexagonal
hcp = hexagonal close packed; lattice constants a and c.
op = simple orthorhombic, monoclinic, triclinic
tp = simple tetragonal
dia = diamond structure
r = trigonal or rhomboedral trigonal

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© H. Föll (Iron, Steel and Swords script)