Which element is the most reactive metal?

Question

Rb or Co, and how do you know?

Thanks in advance.

Answer 1

Rb (alkali metal) has an electronegativity of 0.82, while Co (transitional metal) has an electronegativity of 1.88. Rb is much more reactive.

If you did mean to compare Rb to Cs, then in the alkali group, as we go down the group we have elements Lithium (Li), Sodium (Na), Potassium (K), Rubidium (Rb), Cesium (Cs) and Francium (Fr). They have all only one electron in their outermost shells. All the elements show metallic properties and have valence +1. They give up electrons easily. Reactivity or the ease with which these elements give off their electrons increases with the size of the atoms. The size of the atom increases from Li to Fr. The outermost electron is less loosely bound in Fr than in Li, as in Fr the distance between the last electron and the positive nucleus is large; this makes the attractive force binding or holding the electron to be less. Thus Cs will give up electrons more easily than Rb. This makes Cs more reactive than Rb.

Hope that helps~

Answer 2

Of the two, Rb is the strongest. There is a rule. Watch a periodic table. The reactivity grows as you go down in a column (for example, column II-A: let's take the first 3, Be, Mg and Ca. Ca is the "lowest" of all, so that's the most reactive).

The reactivity also grows as you go to the left in a row. For example, Na, Mg and Al are in the same row, but Na is the closest to the left edge from the three, so Na is the most reactive of the 3.

That's why the alkali metals (first group) are the most reactive column of elements. The elements from the last period are the most reactive of all periods. So, lsearch an alkali metal which is in the last period.

It's francium, but this is radioactive, so Cs is considered to be the most reactive metal. If you put even a very small piece of one of these two metals in water, it will explode. Seriously!
...but they are very hard to find, are in very small quantities, they are very expensive and they are only available for research, just because they are VERY dangerous !
Have a nice day!
Louise B. :))

Answer 3

Caesium. Generally, the reactivity of metals in Group I increases down the group. Hence, Lithium would be the least reactive and Francium will be the most reactive metal. Caesium is below Rubidium in the periodic table, hence Caesium will be the most reactive.

This is why:
The reactivity of an element is determined by how readily it loses or gains electrons to acheive an electronic configuration with 8 outermost electrons. Hence, Group I metals will be the most reactive metals are they only need to lose 1 valence electron to acheeive that electronic configuration. As we go down a group, the number of electron shells increases. Hence, as we go down Group 1, the reactivity of the metals increases as the ease of losing that electron increases. This is beacuse the valence electron( negatively charged) is furthur away from the nucleus( positively charged due to presence of protons). Hence, the electrostatic forces of attraction between the valence electron and the nucleus decreases doen the group.

Therefore, reactivity of Group I metals increases down the group.

Answer 4

Rb is most reactive.

Rubidium Rb : reactivity
Burns vigorously with a red flame when heated in air/oxygen to form the white powder rubidium oxide.
http://www.wpbschoolhouse.btinternet.co.uk/page03/Reactivity.htm

Cobalt is not particularly reactive with air. However on heating the oxide Co3O4 is formed. If the reaction is carried out above 900°C, the result is cobalt(II) oxide, CoO.
http://www.webelements.com/webelements/elements/text/Co/chem.html

Answer 5

Caesium Cs - is extremely reactive, it explodes with cold water forming the alkali Caesium Hydroxide and hydrogen gas.
2Cs(s) + 2H2O(l) → 2CsOH(aq) + H2(g)

It's due to the number of Energy Shells making the outer shell of the element more open to reaction with other elements being less strongly attracted to its Nucleus..
(Francium (Fr), being the last of the Alkali Metals, is, I believe, even more reactive).

(Co, is not an alkali metal).

Answer 6

Rb since its is a metal of first group very reactive and giving a strong base RbOH

Answer 7

definetely rubidium, by looking at the periodic table and the atomic number, it has to be rubidium

colbalt isnt very reactive

Answer 8

most reactive is francium but it is also radioactive.
here is a video
http://www.youtube.com/results?search_type=search_videos&search_query=francium&search_sort=video_view_count&search_category=0&search=Search&v=&uploaded=

Answer 9

I'ts Cesium (Cs).

Answer 10

Metals do not form compounds with each other. They only form compounds with nonmetals. These compounds are ionic compounds based on the electron transfer from metal to nonmetal. If the electron losing tendency of the metal A is greater than that of metal B, then metal A is more active than metal B. The electron losing tendency depends on the ionization energies of metals. The smaller the ionization energy, the easier the removing electron from metal. Then you will ask "what are the factors affecting the ionization energies of the atoms?" The major factor is the size of the atom which is observed in a group of the periodic table. As you go down in a group, the atomic radius increases by the addition of a shell (energy level). The larger the atomic radius, the easier to remove the electron from the valance shell (the outermost shell). Therefore the ionization energy decreases. The other factor is the stability of the atom which is observed in a period of the periodic table. As you go across a period, the size of the atoms decreases from left to right. Therefore, it is expected that ionization energy increases from left to right. It is true for most of the groups, but there are some exceptions. These exceptions are due to the stability of atoms. The most stable atoms are the noble gas atoms. (Full filled outermost shell) E.g. Ar: 1s2 2s2 2p6 3s2 3p6 = 18e- (Group: VIIIA) Second degree stable atoms are the atoms having the full filled outermost subshells. If the outermost subshell of an atom ends with s2, d10 or f14 it is second degree stable atom. (why didn't we write p6? Because in such cases the atom automatically becomes a noble gas atom which is the first degree stable) E.g. Mg : 1s2 2s2 2p6 3s2 = 12 e- (Group IIA) Third degree stable atoms are the atoms having the half filled outermost subshells. If the outermost subshell of an atom ends with s1, p3, d5 or 7 it is third degree stable atom. E.g. P: 1s2 2s2 2p6 3s2 3p3 = 15e- (Group: VA) Therefore, across a period, the ionization of the group IIA is greater than that of the group IIIA. Similarly, the ionization of the group VA is greater than that of the group VIA.