Actinide Series: Elements & Periodic Table

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  • 0:04 Creating New Elements
  • 1:45 The Actinide Series
  • 3:31 Properties of Actinides
  • 4:29 Lesson Summary
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Lesson Transcript
Instructor: Laura Foist

Laura has a Masters of Science in Food Science and Human Nutrition and has taught college Science.

The actinide series includes elements 89-103. In this lesson, we will learn what characteristics these elements share, how they are used, and how they were discovered.

Creating New Elements

Imagine you're walking along a road and notice that the houses are numbered 1, 2, 3..., with each house and number getting bigger and bigger. Then it suddenly stops at 8 and skips up to 10. But there are still empty lots. It is possible to have a number 9 house in one of these empty lots.

This is what happened with many of the 'actinide series' elements. Scientists had discovered the naturally occurring element uranium (atomic number 92) in 1789. By the year 1900 scientists understood that there was an element for each atomic weight, and had developed the periodic table organizing the elements by this characteristic. At this point thorium (atomic number 90) and uranium (92) had been discovered, but they were missing atomic number 91.

Finally, in 1913, protactinium (atomic number 91) was discovered! Scientists then began to wonder if uranium was truly the largest element by atomic weight out there. For the next 30 years, scientists searched for additional elements. Then, in 1940, scientists created the next two elements: neptunium (atomic number 93) and plutonium (atomic number 94). You may have heard about plutonium since it was used in atomic bombs. There have been nine more elements created in the actinide series since then, all between 1944 and 1961

  • Americium, atomic number 95
  • Curium, 96
  • Berkelium, 97
  • Californium, 98
  • Einsteinium, 99
  • Fermium, 100
  • Mendelevium, 101
  • Nobelium, 102
  • Lawrencium, 103

The Actinide Series

The actinide series includes elements with the atomic numbers 89 to 103. It's shown in the bottom row of the periodic table. This row is separated out from the rest of the periodic table because it, along with the lanthanide series, would otherwise make the table very wide. The reason these elements can be broken into a new section is because they are f-block elements. In other words, they use s, p, d, and f orbitals to fill their outer shells.

The actinide series is found below the main periodic table, as the bottom row
Periodic table

Recall that abbreviated electron configurations use the last noble gas and then indicate the electron configuration of electrons beyond the last noble gas. For the actinide series, the last noble gas was radon (Rn).

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