Which element is the most reactive?

Francium is the most reactive element in the Periodic table. This is due to a combination of shielding and distance of valence shell electron from the positively charged nucleus makes it easier for the valence shell electron to be lost in a reaction!

Group 1 of the periodic table includes hydrogen and the alkali metals. Because they have just one valence electron, group 1 elements are very reactive.

Cesium is the most reactive element as its second from the bottom of this group

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.

This question is not as straightforward as it seems. You would need to consider that the Periodic table consists of two groups, non-metals and metals. As both these groups behave very differently it is difficult to directly compare the reactivity and therefore decide which ‘one’ element is the most reactive. The most reactive non-metal is Fluorine. All group 7 elements want to gain one electron to obtain 8 electrons in their outer shell like a stable noble gas element. Fluorine is the most reactive group 7 element as it has the least amount of shells. By having fewer shells the distance between the positive nuclear charge and the attracting electron is shortest. Metals also strive to obtain a stable electronic configuration to its nearest noble gas element but this time by losing electrons. Group 1 metals are the most reactive as they only have one electron to lose. The most reactive metal is Francium as it has the most number of electron shells. This increases the distance between the outer electron which needs to be lost and the attractive positive nuclear charge. 

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.

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.

Francium is the most reactive element, it is at the bottom of group 1 in the periodic table. Because it is in group 1 this means it has 1 electron in its outer shell so to become stable it wants to lose that electron, it is in period (row) 7 it has 7 shells of electrons so that 1 electron that it wants to lose is very far away from the positive nucleus.

A chemical reaction always includes a reshuffle of electrons (which are found in orbiting the positive protons and neutrons in the nucleus). Ionic reactions tend to be more vigorous than covalent. It is easiest for an atom to lose an electron (therefore easier for it to react/be more reactive) if there is only one electron in the outer shell and there is a big distance from the nucleus. Therefore, all group 1 elements are the very reactive (they all have 1 electron in their outer shell) but Francium is the most reactive (it has the most number of electron shells therefore there is a greater distance between the outer electron and the nucleus). Similarly, the elements that find it easiest to gain an electron are those with 7 electrons in their outer shell (all elements in group 7 as they really want to have 8 electrons in their outer shell). However, in this 'gaining electron' scenario, the most reactive element in group 7 is the one with the fewest electron shells. This is because the electron is attracted by the positive nucleus so the shorter the distance to the nucleus, the better. The most reactive group 7 element is Fluorine.

fluorine is the most reactive element

fluorine is the most reactive.

Francium is most reactive element in periodic table.

Caesium (Cs) - a group 1 alkalki metal. All alkali metals are reactive, increasing as you go down the periodic table.

potassium is the most reactive element

The group 1 elements are the most reactive going in down the column from least to most