[Rn] 7s² 5f¹² corresponds to which element?

The electron configuration [Rn] 7s² 5f¹² indicates the distribution of electrons in an atom. Let's break it down. The notation [Rn] represents the electron configuration of radon, which accounts for the electron shells up to radon, that is, the core electrons. The notation that follows, 7s² 5f¹², describes additional electrons.

In this configuration, the 7s² signifies that there are two electrons in the 7s subshell. The 5f¹² means that there are twelve electrons occupying the 5f subshell.

When looking at the actinides and transactinides, the elements in the f-block, specifically those filling the 5f subshell, range from elements 96 (curium) to 103 (lawrencium). In this range, the element with the configuration that includes 12 electrons in the 5f subshell corresponds to the element mendelevium (Md), which has the atomic number 101. However, the correct element corresponding to [Rn] 7s² 5f¹² is actually nobelium (No), with an atomic number of 102.

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