Which of the following element has atomic number 87?

Francium

The correct answer is option 1. Francium.

Francium is a chemical element with the symbol Fr and atomic number 87. It is a highly radioactive metal and is part of the alkali metal group. Francium is extremely rare in nature due to its short half-life; most of its isotopes have half-lives of a few minutes or less. Because of its radioactivity, large-scale studies of francium's properties and behavior have been challenging.

The alkali metal group includes elements like lithium (Li), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), and francium (Fr). Francium is the least stable of the alkali metals, and its scarcity and radioactivity make it difficult to study in detail.