Americium and Curium

Americium (²⁴¹Am) is used as a diagnostic aid for analysis of bone and mineral conditions.

Curium discovered by Glenn Seaborg and co–workers in 1944 was named in the honour of Pierre and Marie Curie. It has a use in satellite technology. It is a toxic substance due to its radioactivity.

Americium (₉₅Am): This element is prepared by the bombardment of with the α‐particle which on subsequent emission of neutron and β‐particle will result in

Curium(₉₆Cm): Curium is obtained in similar fashion to that of Americium but by bombardment of with α particle.

Berkelium and Californium

Berkelium : Berkelium was named after the town Berkley, California, where it was first made. A radioactive, silvery metal obtained from plutonium in nuclear reactors. Less than a gram is made each year. Because of its rarity, berkelium has no commercial or technological use at present. Berkelium is made in milligram quantities only by the neutron bombardment of plutonium.

Californium : Californium–249 atoms had been bombarded with calcium–48 ions to produce ununoctium (element 118) the heaviest chemical element synthesized so far.

Next two elements are Berkelium (₉₇Bk) and Californium (₉₈Cf). These are produced in the following reactions:

₉₅Am²⁴¹ + ₂He⁴ ₉₇Bk²⁴³ + 2 ₀n¹

Berkelium decays by K electron capture to give Cm.

₉₇Bk²⁴² ₉₆Cm²⁴³ (by k electron capture)

₉₆Cm²⁴² + ₂He⁴ ₉₈Cf²⁴⁴ + 2 ₀n¹

Californium decays by α‐particle emission to give Cm.

₉₈Cf²⁴⁴ ₉₆Cm²⁴⁰ + ₂He⁴

Bk has five isotopes with mass equal 243, 244, 245, 249, 250. Longest lived is Bk²⁴⁹ with average life of 1 year.

Cf has eight isotopes with mass equal to 244, 246, 248 to 253. The longest life is 500 years for Cf²⁴⁹.

Einsteinium Einsteinium was discovered unexpectedly along with fermium in debris from the first large hydrogen bomb test, which took place in the Pacific on October 31 1952.

Einsteinium (₉₉Es): For production of heavier elements, heavier projectiles such as N and O ions have been used in specially designed accelerators. Ex: Element number 99 named Einsteinium (Es) was obtained by the bombardment of U²³⁸ with ₇N¹⁴ ions.

₉₂U²³⁸ + ₇N¹⁴ ₉₉Es²⁴⁷ + 5 ₀n¹

Fermium(₁₀₀ Fm): Element number 100, named Fermium (₁₀₀Fm) was discovered in the below reaction–

₉₂U²³⁸ + ₈O¹⁶ ₁₀₀Fm²⁵⁰ + 4 ₀n¹

It has a life period of about 3 hrs. Its other isotopes have masses 254, 255 and 256.

Discovery of Mendelevium Many transuranium elements including mendelevium were discovered using the 60-inch cyclotron at the University of California Lawrence Radiation Laboratory, Berkeley.

Mendelevium (₁₀₀Md): Atomic number of this element is 101. It is prepared by the bombardment of ₉₉Es²⁵³ with α‐particles of high energy.

₉₉Es²⁵³ + ₂He⁴ ₁₀₁Md²⁵⁶ + ₀n¹

Nobelium (₁₀₂Nb): The atomic number of this element is 102 and is obtained by bombarding ₉₆Cm with ₆C¹² ions. It has been named as Nobelium (₁₀₂No) in the honour of Alfred Nobel, inventor of dynamo.

₉₆Cm²⁴⁶ + ₆C¹² ₁₀₂No²⁵² + 6 ₀n¹

Lawrencium Lawrencium is produced for example by bombarding californium with boron or americium with oxygen.

Lawrencium (₁₀₃Lw): Recently element number 103 named Lawrencium (₁₀₃Lw) has been synthesised by the reaction.

₉₈Cm²⁴⁴ + ₅B¹⁰ ₁₀₃Lw²⁵³ + ₀n¹

The transactinide elements begin with rutherfordium (atomic number 104). They have only been made artificially, and currently serve no practical purpose because their short half‐lives cause them to decay after a very short time, ranging from a few minutes to just a few milliseconds (except for dubnium, which has a half life of over a day), which also makes them extremely hard to study.