Actinium

Its chemistry is dominated by (+3) O. S.
Its compounds are colorless.
There are 29 known isotopes.
It does not have absorption in the UV visible region between 400-1000nm.
227Ac is strongly radioactive and so are its decay components.
Actinium metal is silvery solid; obtained by reduction of oxide, fluoride or chloride w/ Group 1 metals; and oxidized rapidly in moist air.
It forms insoluble fluoride and oxalate (Ac2(C2O4)3*10H2O) compounds

Thorium

It exhibits the +4 O.S. exclusively.
The chemistry in the +2 and +3 O.S. is restricted to iodides like ThI2 and cyclopentadienyl Th(C5H5)3.
It has wide coordination chemistry with oxygen donor ligands.
Thorium metal is bright and silvery-white and tarnishes to a dull black color when exposed to air. It is soft enough to be scratched with a knife and melts at 1750°. It slowly dissolves in dilute with hydrogen evolution and can be pyrophoric as a powder.

Protactinium

It has been in existence longer than any other actinide.
231Pa has a half-life of 3.28*1014 which allows it to make chemical study easy for it.
It has α-emission, so it has appropriate radiochemical precautions.
The Pa metal is malleable, ductile, silvery, and has a melting point of about 1565°C. It is also a superconductor.

Uranium

Many compounds exist between the O.S. of +3 to +6.
The main O.S. are +4 and +6.
Stability of O.S.

U3+ reduces to hydrogen
U4+ stable in aqueous solution in the absence of air
U5+ disproportionates rapidly into a mixture of U4+ and U6+ in aqueous solutions
U6+ stable in aqueous solutions

When pure it has a silvery appearance.
When attacked by air, yellow film then black coating develops, it is a mix of oxide and nitride.
Powder metal is pyrophoric in air.
Reacts readily with hot water to prevent substances from coming into contact in nuclear reactors

Neptunium

It was the first transuranium element to be discovered in 1940.
There are 15 known isotopes, only 237Np, w/ half-life of 2.14*106 years, is useful for chemical experiments.
It exhibits O.S. of +3 to +7 in compounds.
It is a silvery metal, with a melting point of 637°C and a boiling point of 4174°C.
It has surface oxidation when exposed to air.
It is converted to NpO2 at high temperatures.

Plutonium

There are 15 known isotopes.

The masses range from 232 to 246.
The most important isotope is 239Pu because it is fissionable and has a half-life of 24,100 years, which makes it easy for chemists to study.

It exhibits O.S. from +3 to +7.

The +3 and +4 O.S. are the most important, but compounds of the ions are well defined.
Pu+7 only exists under very alkaline conditions.

It has 6 allotropic metal forms, which makes it unusual.

They can form at normal pressure between room temperature and its melting point, 640°C.
It is dense, silvery and a reactive metal; more reactive than uranium or neptunium.
When attacked by air, it forms a green-gray oxide coating.
It reacts slowly with cold water, faster with dilute H2SO4, and dissolves quickly in dilute hydrochloric acid or hydrobromic acid.

Americium

It has 12 known isotopes.
It was first made in 1944-1945 by Seaborg and his coworkers, where they decayed 239Pu and 241Pu to 241Am, which has a half-life of 433 years.

241Am and 243Am, which has a half-life of 7380 years are the most important isotopes, because their half-lives allow scientists to study their characteristics.

The metal is a slivery, ductile and very malleable.

It tarnishes in air slowly and dissolves in dilute hydrochloric acid quickly.
It reacts with heating with oxygen, halogens, and other nonmetals

Later Actinides (Cm, Bk, Cf, Es, Fm, Md, No, and Lr)

Their chemistry is of mostly the M+3 state.
They all form binary compounds, such as trihalides.
Curium, berkelium, and californium have the following chemistry:

Oxidized by air to the oxide
Electropositive
Reacts with hydrogen on warming to form hydrides
Yields compounds on warming with group 5 and group 6 non-metals