I have chosen to write about americium, I had noticed that no posts entitled americium existed on wordpress. Americium is one of my personal bests in terms of Z (number of protons). The element which the highest Z I have ever seen is plutonium, the highest Z I have been in the same room as is californium while the highest Z I have ever used in an experiment which I did myself is americium.
Americium is a element which can not make up its mind, in some ways it is like a lanthanide. It has a very insoluble fluoride and it extracts with bis-2-ethylhexyl hydrogen phosphate into alkane diluents while on the other hand it thinks it is a transition metal. It is more able to bind to nitrogen donors than a lanthanide and it is isoelectronic with uranium(0).
Uranium(0) complexes of cyclopentadienyl ligands are able to bind to carbon monoxide in a similar way to a transition metal. Thus uranium(o) is like a transition metal.
Also americium(III) is coloured, it is pink in colour while the lanthanides are almost perfectly colourless. The formation of coloured metal cations is very much a transition metal thing. For example copper(II) in water is blue while nickel(II) in water is green. Iron(III) is a funny one, in acidic water it is a pale purple but in water it undergoes hydrolysis to form a dark brown complex.
I may well write some more about americium in the near future.