Which element is the most reactive?

Fluorine is the most reactive element due to its high electronegativity

The periodic table has two groups; metal and non-metal elements and so to answer your question I will focus on each group and identify the most reactive element out of each group. The most reactive element is Fluorine in the non-metals group and Caesium in the metals group. Due to both these elements being different 'types' of elements it is difficult to make a comparison of reactiveness and state which one is more reactive. Thus, each one must be seen as being the most reactive in their own groups. I hope that helps!

Aluminium is the most reactive element it's atomic number is 13. Al is its symbol. Finally, the most reactive elementary group is alkali metals situated far apart from intermediate metals and noble gases.

My favourite element which is Fluorine.

Caesium is the most reactive metallic element, although theoretically Francium would be if it wasn[t so radioactive and conseqently so rare. Flourine is the most non-metallic element.

Flourine is the most react element in the period table, this is due to it having an almost full outer electron shell of 7 electrons, its outer most shell being closer to the nucleus than other elements in Group 7. It is also the most electronegative element in the table, meaning it will react violently with elements in Group 1 & 2, as they are electropositive.

fluorine is the most reactive.

Fluorine (F) is identified to be the most reactive element in the periodic table. It's need to gain an electron to form a a full outer shell (2,8) gives rise to it being the most reactive.

Sodium (Na) is the most reactive element since it’s valence electrons are not tightly held together in the atom. It’s atomic number is 11, therefore when writing the electron configuration (2,8,1), the last electron which is 1 is the valence electron which is easily lost to other ions for stability.

K (Potassium) is the most reactive element. It stays at the top of the periodic table. It can lose its valence electron easily hence it's the most reactive element.

Alkali metals is the most reactive element

fluorine is the most reactive element

So, this question really depends on the scenario involved, but essentially we need to think about what does reactivity mean? For a metal that typically means how readily does it lose an electron, for a non-metal how readily does it gan an electron. As you go down a group, the atoms get larger and have a weaker attraction to their outermost electrons - which means that metals get more reactive and non-metals get less. So, this would mean Fluorine is the most reactive non-metal (horrible stuff, chlorine was bad enough in the trenches, fluorine is significantly worse) and Francium for a metal. Francium is radioactive though, with the most stable isotope only having a half-life of 21.8 minutes, so although it is very reactive, it decays so this probably a moot point.

Fluorine as it just need one electron to form a full outer shell

In terms of a metal then Group 1 Francium would be most reactive. but, it's very rare and highly radioactive. For a metal in group 1 you would have heard of it would be Caesium. In terms of a non-metal it would be group 7 fluorine.