Subject
nickel
3
niobium
osmium
3
palladium
3
platinum
3
ruthenium
3
actinide
2
chromium
2
cobalt
2
hafnium
2
iron
2
lanthanum
2
manganese
2
metal organic compound
2
molybdenum
2
rhenium
2
rhodium
2
tantalum
2
technetium
2
titanium
2
tungsten
2
vanadium
2
zirconium
2
chemical reaction
1
nitrogen
1
oxygen
1
phosphorus
1
potassium
1
praseodymium
1
radium
1
rare earth
1
rare earth compound
1
rare earth organic compound
1
rhenium compound
1
rubidium
1