Question

СРОЧНО-ПРЕСРОЧНО! химический элемент 3 группы периодической системы радиоактивный металл, актинид

Answer 1

Актиний (Ac), из группы Актиниды (актиноиды).

Answer 2

Chemical Element of Group 3 in the Periodic Table

The chemical element of group 3 in the periodic table that is a radioactive metal and an actinide is Actinium (Ac).

Actinium is a silvery, radioactive, metallic element. It is the first member of the actinide series, which is a group of 15 similar elements in the periodic table. Actinium is found in uranium ores and is used in neutron production and as a radiation source in radiotherapy for cancer treatment.