Actinium

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This editable Main Article is under development and subject to a disclaimer.

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| Actinium | 227 |

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| Ac

1s22s22p63s23p63d104s24p6 4d105s25p64f145d106s26p66d17s2 |
[ ? ] | Transition metal:

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Actinium is a chemical element, having the chemical symbol Ac. Its atomic number (the number of protons) is 89. It has a standard atomic weight of 227 g•mol −1 and it is a solid in its elemental form.

Actinium is considered a member of the "Transition metal" class of elements. At a pressure of 101.325 kPa, it has a boiling point of 3,198 °C and a melting point of 1,051 °C.

## History[edit]

Actinium has been discovered in 1899 by André-Louis Debierne, and independently by F. Giesel in 1902. This element was named from the Greek word aktis, aktinos (ακτίς, ακτίνος), meaning beam or ray.[1]

## References[edit]

1. ↑ William M.Haynes (2010). Handbook of Chemistry and Physics, 91st Edition. CRC Press. ISBN 1-4398-2077-5.