Room of the Elements · No. 88

Radium (Ra): what kind of element is it?

In short

Radium is element number 88, with the symbol Ra. Its name comes from the Latin word for “ray.”

Atomic number 88(226)

RaRadiumラジウム (rajiumu)

Symbol: Ra
Atomic weight: (226)
Place in the table: Period 7 · Group 2

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)”.

Discovered by the Curies

In 1898, Pierre and Marie Curie found two new radioactive elements, polonium and radium, in an ore called pitchblende.

Mendeleev, creator of the periodic table, visited the Curies, confirmed the radioactive elements for himself, and revised his periodic table the next year.

Where it sits on the table

Radium is in the seventh row of Group 2, at the bottom of the column with magnesium, calcium, strontium and barium.

Think about it

Q1How do you think radioactive elements were told apart?
Q2Radium’s name later became the basis for radon’s. What do you think of names linking up like this?
Q3Can you name the Group 2 elements from the top?

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

Did you know? — The Curies’ name lives on in element 96, curium.

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). The Curies’ discovery and Mendeleev’s visit: “International Year of the Periodic Table 2019 (150 years of the periodic table),” Kagaku to Kyōiku 67(6), 2019. All sources are in Japanese.
Written by CCN CO., LTD.

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