Question

Which of the following is the most active metal?
(A) Lithium
(B) Sodium
(C) Potassium
(D) Rubidium

Answer 1

Hint- In order to solve the given problem, we will first see the characteristics on which the activity of metal depends upon. Then we will check for the series of activity of the metals and also the trend followed by different metals in the row of the periodic table; we will further see the different characteristics of active metals.

Complete answer:

Activity of metals depends on the basis of ease on which it can undergo any sort of reactions may it with basic abundant substances like oxygen and water as well.
We have four classes of metals on the basis of its activity. They are:
Class I Metals: The Active Metals
Li, Na, K, Rb, Cs (Group IA)
Ca, Sr, Ba (Group IIA)
Class II Metals: The Less Active Metals
Mg, Al, Zn, Mn
Class III Metals: The Structural Metals
Cr, Fe, Sn, Pb, Cu
Class IV Metals: The Coinage Metals
Ag, Au, Pt, Hg
The periodic table contains different elements arranged according to the activity of the elements. In the periodic table as we move from right row to left row the activity of the elements increases eventually; so the first group metals or the alkali metals are the most reactive ones.
Also in the periodic table as we move down in the row, the activity of the metals increases so the metals at the end of the row are the most active ones.
So, as all the metals listed in the options belong to group 1 so the activity of the element at the bottom amongst the given ones will be most active.
The listing of the element is:
Lithium< Sodium< Potassium< Rubidium
Hence, rubidium is the most active amongst the given options.
So, the correct answer is option D.

Note- On the periodic table the most reactive element is the francium. But Francium is a laboratory-produced element and only minute amounts have been made, so the most reactive metal is cesium for all practical purposes. Cesium reacts explosively with water while francium is expected to react much more vigorously.
The most active metals are so reactive that they are readily mixed with the ambient oxygen and water, and are thus contained in an inert liquid such as mineral oil. Second-class metals are only slightly less involved. They don't react at room temperature with water but they react with acids quickly. The third class contains metals which react with only strong acids. Fourth class metals are so unreactive at room temperature they are basically inert.