Naming ionic compounds
Ruby, 114

f,s=$*[0].split /\d*(?=[A-Z]|\Z)/
puts (n=Hash[*&lt;&lt;X.split-%w[0 1]].invert)[f]+" "+n[s].sub(/(i..|.gen|..)\Z/,"ide")
Hydrogen H 0
Helium He 0
Lithium Li 1
Beryllium Be 1
Boron B 0
Carbon C 0
Nitrogen N 0
Oxygen O 0
Fluorine F 0
Neon Ne 0
Sodium Na 1
Magnesium Mg 1
Aluminium Al 1
Silicon Si 0
Phosphorus P 0
Sulfur S 0
Chlorine Cl 0
Argon Ar 0
Potassium K 1
Calcium Ca 1
Scandium Sc 1
Titanium Ti 1
Vanadium V 1
Chromium Cr 1
Manganese Mn 1
Iron Fe 1
Cobalt Co 1
Nickel Ni 1
Copper Cu 1
Zinc Zn 1
Gallium Ga 1
Germanium Ge 1
Arsenic As 0
Selenium Se 0
Bromine Br 0
Krypton Kr 0
Rubidium Rb 1
X


Uses a paste of the element text that I haven't counted in the score. I remove the metal tag (since I'm assuming the compounds are always given with the metal first, so I don't actually need it) and build a dictionary with it. I identify the part to replace with "ide" by checking the end of the string for three letters starting with i, four letters ending with gen, or otherwise just the last two characters.