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95
Room of the Elements · No. 95

Americium (Am): what kind of element is it?

日本語

In short

Americium is element number 95, with the symbol Am. Its name comes from America.
Atomic number 95(243)
AmAmericium (amerishiumu)
Symbol
Am
Atomic weight
(243)
Place in the table
Period 7 · Actinoids

The number in parentheses is not an atomic weight. It is the mass number of one radioactive isotope of the element.

Atomic weight from the Chemical Society of Japan, “Table of Standard Atomic Weights with Four Significant Figures (2026)”.

A continent’s name

Americium was discovered in 1945 and named after America. Directly above it on the table is europium, “Europe.” Two continents line up vertically.

Where it sits on the table

The fifteen elements from actinium to lawrencium are called the actinoids. On the Room of the Elements table they are in the lower of the two rows set apart at the bottom.

Think about it

There is no single right answer. Talking it over with someone at home is a good way to learn.

Did you know? — Element names linked to America: americium (America), berkelium (Berkeley) and californium (California).
Next steps
About this page
Symbol and atomic weight: Chemical Society of Japan, “Table of Standard Atomic Weights (2026)” and “Table of Atomic Weights with Four Significant Figures (2026)”. Origin of the symbol and year of discovery: Sugiyama, “The Origins of Element Symbols,” Kagaku to Kyōiku 43(12), 1995 (Chemical Society of Japan). All sources are in Japanese.
Written by CCN CO., LTD.
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