STABLE all the way!
The most reactive elements are alkali metals and halogens.
Chlorine is the most reactive gas element. Chlorine is in the halogen family.
Less reactive elements are more likely to be found uncombined, that is as the element rather than as part of a compound. This is usually called being 'found native'. For instance gold mines contain actual pieces of gold, whereas an iron mine usually contains something like rust, which has to be converted by a chemical reaction to obtain the metal.
The investigator will discover that potassium (K) is much more reactive than silver (Ag). Silver is a transition metal (d block elements) while potassium is an alkali metal. The alkali metals are in Group 1 of the periodic table, and elements on the left side (and going down) are quite a bit more reactive than those in the middle, where silver is. It turns out that potassium has a lone valence electron, and this element want to loan that electron out in a chemical bond very badly. That makes potassium much more likely to form a chemical bond than silver, and makes it more reactive.
Helium, neon and argon are the least likely elements to form compounds.
The elements in Group 1 of the Periodic Table are highly reactive in water, and, only slightly less reactive in Oxygen. Group 2 elements are also quite reactive in Oxygen, but not quite as reactive as those elements in Group 1.
The most reactive elements are alkali metals and halogens.
Francium and Flourine are the most reactive elements. Francium is at the bottom, Flourine is at the top. The trend isn't as simple as your question. Elements towards the top of the table "want" electrons more. This means they are less likely to give them up and more likely to "steal." In terms of reactivity, this means that the metals at the top are less reactive and the non-metals at the top are more reactive.
It doesn't seem likely. Selenium isn't terribly reactive, and selenium monochloride exists in equilibrium with a different kind of selenium chloride, chlorine gas, and elemental selenium; this indicates that there's not a huge energy difference between the uncombined elements and the compound, as you would expect there to be if they "blew up" when combined.
The alkali metals like sodium,pottasium etc.are very much reactive.Francium is so far the most reactive alkali metals.
differences in chemical reactivity, the more reactive the more likely to form compounds
These elements in pure form are extremely reactive. It is hard to create and maintain the pure environment necessary to maintain their purity.
Chlorine is the most reactive gas element. Chlorine is in the halogen family.
Far left. Depends on what you mean by far right. If you mean the halogens - fluorine, chlorine then they are also very reactive like the alkali metals on the far left - lithium, sodium, potassium etc. One big difference is the alkali metals get more reactive as they get bigger and the halogens are more reactive as they get smaller.
The three most general elemental groups are nonmetals, semimetals, and metals. The characteristics you've described fit the "metals" group of elements.
The reactivity of halogens decreases down the group, which means Fluorine is the most reactive halogens as it is the most electronegative elements among the halogens, and also the Periodic Table.
No, they are not likely to bond. Neon has a complete octet and is not reactive.