Actinide Characteristics

Like lanthanides, actinides are 15 chemical elements that share characteristics common, for which they are classified in a special category at the bottom of the Table periodic.

Actinide characteristics:

They are located in period 7 of the periodic table.

They cover 15 elements, from 89 to 103.

They share the structure of Actinium.

The electrons that increase in each element do so mainly at the 5f energy level, which is less chemically reactive.

They are also called rare earths, because in the natural state they are always combined to form oxides.

The heaviest elements, from Curium, have been produced in the laboratory, since they do not exist in nature.

Although they have variable valences, most have +3 and +4 valences.

As its atomic number increases, its radius decreases.

They are all radioactive.

The actinides are:

Actinium (Ac).

Atomic number 89

Atomic Weight: 227

Solid state

Appearance: soft metallic, glow in the dark

Valencias: +3

Melting point: 1050 ° C

Boiling point: 3198 ° C

It was discovered in independent research in 1899 and 1902. It is a high-level radioactive element, so its uses are mainly for research, as a proton emitter. It is also used in medicine, for radiotherapy, producing an isotope of bismuth that reacts with some cancer cells. However, due to its radiation level, an overexposure or some accidental exposure can cause radiation to affect the cells of the immune system, destroying them.

Thorium (Th)

Atomic number 90

Atomic Weight: 232

Solid state

Appearance: Metallic, silver gray.

Valencias: +3, +4

Melting point: 1756 ° C

Boiling point: 47.88 ° C

It was discovered in 1828 and its radioactive properties were described at the end of the 19th century. In its radioactive decomposition it degrades into radio and finally lead. Its oxides are used in the industry combined with tungsten, to make filaments of incandescent bulbs, and combined with Tungsten, to reduce the temperature of melting and boiling in some welding procedures, mainly the Tig (tungsten inert gas) and GTAW (gas arc welding) procedure. tungsten). Regarding its radioactive properties, it is used mainly as an emitter of alpha particles.

Protactinium (Pa)

Atomic number 91

Atomic Weight: 231

State: Soft solid

Appearance: Metallic, silvery white

Valencias: +3, +4, +5, +2

Melting point: 18840 ° C

Boiling point: 4027 ° C

It was predicted in 1871 and identified in 1913. Due to its scarcity and high level of radioactivity, its uses are limited to scientific research.

Uranium (U)

Atomic number 92

Atomic Weight: 238

Solid state

Appearance: Grayish metallic

Valencias: +6, +5, +4, +3

Melting point: 1132 ° C

Boiling point: 4131 ° C

It was discovered in 1789. It is a rare metal, which in its natural state is combined with other minerals. Its most stable form is isotope 238, which has a very long decomposition period, and is not easily modified when bombarded with protons. As nuclear fuel, isotope 235 is mainly used. This isotope also has the characteristic of producing a fission chain reaction. When radioactive material is low in Uranium 235, it is called Depleted Uranium, which has been used to make bullets. that long after they have been fired, they continue to have effects of radioactive contamination of land, water and food. It also causes cancer in people who were injured, handled or had contact with these projectiles. The Hiroshima atomic bomb was a uranium bomb.

Neptunium (Np)

Atomic number 93

Atomic Weight: 237

Solid state

Appearance: Shiny metallic

Valencias: +5 (the most stable) +3, +4, +6, +7

Melting point: 637 ° C

Boiling point: 4000 ° C

It is a synthetic, radioactive element, obtained for the first time in 1940, after bombarding Uranium. Subsequently very small quantities have been found in deposits of Uranium. However, it is obtained mainly as a by-product of the manufacture of the plotonium 239 isotope.

Plutonium (Pu)

Atomic number 94

Atomic Weight: 244

Solid state

Appearance: Metallic, silvery white

Valencias: +4 (the most stable), +6, +5, +3

Melting point: 639 ° C

Boiling point: 3232 ° C

It was produced in 1940, and like uranium, its isotope 239 has the characteristic that when it is bombarded it produces a chain reaction, which releases a large amount of energy. This characteristic was used to make the atomic bombs that the United States dropped on the population of Japan. The bomb dropped on Nagazaki was a Plutonium bomb.

Americio (Am)

Atomic number 95

Atomic Weight: 243

Solid state

Appearance: Metallic, silvery white

Valencias: +3 (main), +7, +6, +5, +4, +2

Melting point: 1176 ° C

Boiling point: 2607 ° C

This element was discovered in 1944, by bombarding Plutonium with neutrons inside a nuclear reactor, a procedure for which its discoverer obtained the patent, as well as that of the element. It is an element that emits gamma rays under normal conditions, which is why it was used as a portable source to take X-rays. It was also used in the past in some smoke detectors, which although the amount of americium was not dangerous to health, were more expensive and were withdrawn from the market.

Curium (Cm)

Atomic number 96

Atomic Weight: 247

Solid state

Appearance: Metallic, silvery white

Valencias: +3

Melting point: 1340 ° C

Boiling point: 3110 ° C

Curium is also a synthetic element, obtained in the laboratory. It is very similar to lanthanides, with the difference that it is radioactive. Due to its atomic degradation with heat release, its possible application for portable thermoelectric generation has been considered.

Berkelium (Bk)

Atomic number 97

Atomic Weight: 247

Solid state

Appearance: Metallic, silvery white

Valencias: -

Melting point:

Boiling point:

It was discovered in 1949 and is produced in a laboratory. However, it is a very rare element, since less than a gram has been produced since its discovery. Its use is mainly for studies on radioactivity and transmutation of matter. It is radioactive, but relatively safe, since it only emits electrons; however, it has a very short half-life (approximately 300 days) and is degraded in Californium, which is very radioactive and dangerous to health.

Californium (Cf)

Atomic number 98

Atomic Weight: 251

Solid state

Appearance: Metallic, silvery white

Valencias: +3 (main), +2, +4

Melting point: 900 ° C

Boiling point: 1470 ° C

It was discovered and synthesized in 1950. It is also the heaviest chemical element that forms naturally on earth. Due to its radioactivity and its characteristics, it is used as a lighter for the ignition of reactors. nuclear, and is also used to create, by atomic bombardment, the rest of the elements of greater mass atomic. It is a dangerous element in case of accidental exposure, since it tends to accumulate in the bones and stop the hematopoietic function (formation of red blood cells).

Einsteinium (Es)

Atomic number 99

Atomic Weight: 252

Solid state

Appearance: Metallic, silvery white

Valencias: +3 (main), +2, +4

Melting point:

Boiling point:

It was discovered in 1952, as a residue from the hydrogen bomb dropped in the Pacific. Its only applications are in research.

Fermium (Fm)

Atomic number 100

Atomic Weight: 257

Solid state

Appearance:

Valencias: +3

Melting point:

Boiling point:

It was discovered in 1952, as a residue from the hydrogen bomb dropped in the Pacific. Its only applications are in research.

Mendelivio (Md)

Atomic number 101

Atomic Weight: 258

Solid state

Appearance:

Valencias: +3

Melting point: 827 ° C

Boiling point:

It was synthesized in 1955. It was created in the laboratory, it is very rare and has no industrial applications.

Nobelium (Nb)

Atomic number 102

Atomic Weight: 259

Solid state

Appearance: Metallic, silvery white

Valencias: +2 (main), +3

Melting point:

Boiling point:

It was synthesized in 1966, in Russia. It has only been obtained at the atomic level.

Lawrencio (Lr [before Lw])

Atomic number 103

Atomic Weight: 262

Condition: Possibly solid

Appearance:

Valencias:

Melting point: 1627 ° C

Boiling point:

It was discovered in 1961. It is a very short-lived chemical element that is produced in the laboratory, obtaining very small amounts.