The cretaceous-tertiary extinction, the most famous of all the big five, has been attributed to what major event that triggered the fall of the dinosaurs?

meteorite or comet impact

Explanation:

The Cretaceous-Tertiary extinction is not the most devastating one that happened, but because of the organisms that got extinct are very well known and famous, it too became the most famous extinction. The reason for the extinction was an impact of a meteorite or comet where Yucatan is located in the present. The impact was so strong that the energy released from it wiped out everything in the surrounding area. But that was not all, as this impact also caused large scale wildfires, activated most of the volcanoes on the planet, triggered enormous tsunami, and a very hot air mass circled the whole planet and fried everything that was not sheltered. The dust, ashes, and other particles released into the atmosphere blocked the sun for a long period of time. the end result was the extinction of lot of animals and plants, most noticeably the dinosaurs.

the seeing the electronic configuration we can say that the element is fluorine.

fluorine is the most electronegative element in the periodic table.

but by only seeing the configuration we cannot say about its reactivity because we don't know if its configuration after excitation or by addition of electrons.

but if not then, it is the lightest halogen and exists as a highly toxic pale yellow diatomic gas at standard conditions. as the most electronegative element, it is extremely reactive: almost all other elements, including some noble gases, form compounds with fluorine.