Postactinoid elements

You have seen that elements with atomic number greater than 92 are called 'Transuranium'. Elements from atomic number 93 to 103 are now included in the actinoid series, and those from 104 to 118 are called postactinoid elements. The postactinoid elements that are known so far are transition metals. They are included as postactinoids because, similar to actinoid elements, they can be synthesized in nuclear reactions. So far, nine postactinoid elements have been synthesized. It is difficult to study their chemistry owing to their short half-lives (the book prints "owing their"). For example, element 112 has a half-life of only 2.8 x 10⁻⁴ seconds — with half-lives of milliseconds, only a little is known about the chemistry of these elements (the book prints "miliseconds").

Rutherfordium forms a chloride, $\mathrm{RfCl_4}$, similar to zirconium and hafnium, in the +4 oxidation state. Dubnium resembles both a group 5 transition metal, niobium(V), and an actinoid, protactinium(V). …