Understanding the Actinide Powering Satellites

The question asks to identify an actinide element, discovered by Glenn T Seaborg in 1940, that is used as a heat source for sensitive electrical components in satellites and also as a power source for satellites.

Let's analyze the key criteria mentioned:

• It must be an actinide.
• It must have been discovered in 1940.
• It must have been discovered by Glenn T Seaborg (or his team).
• It must be used as a heat and power source for satellites.

Evaluating the Options

We are given four options:

1. Nobelium
2. Curium
3. Americium
4. Plutonium

Let's examine each option based on the criteria:

Nobelium ($\text{No}$)

Nobelium is an actinide. However, its discovery is generally recognized in 1966 by scientists at the Joint Institute for Nuclear Research in Dubna, Russia, although earlier claims were made. This discovery year does not match the criteria of 1940.

Curium ($\text{Cm}$)

Curium is an actinide. It was discovered in 1944 by Glenn T. Seaborg, Ralph A. James, and Albert Ghiorso at the Metallurgical Laboratory at the University of Chicago. While discovered by Seaborg's team, the discovery year (1944) does not match the criteria of 1940.

Americium ($\text{Am}$)

Americium is an actinide. It was discovered in 1944 by Glenn T. Seaborg, Leon O. Morgan, Ralph A. James, and Albert Ghiorso at the Metallurgical Laboratory at the University of Chicago. Similar to Curium, the discovery year (1944) does not match the criteria of 1940.

Plutonium ($\text{Pu}$)

Plutonium is an actinide. The isotope Plutonium-239 ($\text{Pu-239}$) was first produced and identified in 1940-1941 by Glenn T. Seaborg, Edwin McMillan, Joseph W. Kennedy, and Arthur Wahl at the University of California, Berkeley. Plutonium is widely used as a heat source and a power source in satellites, specifically the isotope Plutonium-238 ($\text{Pu-238}$). $\text{Pu-238}$ decays with a half-life of 87.7 years, releasing significant heat through alpha decay. This heat can be converted into electrical power using Radioisotope Thermoelectric Generators (RTGs), which are used in deep-space probes and some satellites where solar power is not feasible or sufficient. The discovery period (1940) and the discoverer (Glenn T Seaborg's team) match the criteria.

Summary Comparison

Based on the analysis, Plutonium is the only actinide among the options that fits all the described criteria: discovered around 1940 by Glenn T. Seaborg's team and used as a heat and power source for satellites (specifically the $\text{Pu-238}$ isotope).

Revision Table: Actinides & Discovery

Additional Information: Plutonium in Satellites

Plutonium-238 ($\text{Pu-238}$) is a crucial fuel for Radioisotope Thermoelectric Generators (RTGs). These devices convert the heat released by the decay of a radioactive isotope into electricity using the Seebeck effect (a thermoelectric phenomenon). $\text{Pu-238}$ is preferred for space applications due to several factors:

• High power density: It produces a significant amount of heat per unit mass.
• Suitable half-life: 87.7 years is long enough to power missions lasting decades but short enough to provide a useful power output.
• Manageable radiation: Primarily emits alpha particles, which are relatively easy to shield compared to beta or gamma emitters.
• Reliability: Provides a steady, reliable power source independent of sunlight, essential for deep-space missions or those operating in shadowed regions.

RTGs powered by $\text{Pu-238}$ have been used on numerous successful space missions, including the Voyager probes, Galileo, Cassini, New Horizons, and the Curiosity and Perseverance Mars rovers.