Question

How you would organize the following metals from most active to least active, the most active metal being the top?
Potassium
Aluminium
Nickel
Mercury

Answer 1

Hint:Reactivity can be understood by simple definition of how an atom reacts with another substance. It is just how much energy is required to remove an electron from the outer shell that is ionization energy and how much any atom wants an electron from another atom that is electron affinity. In the modern periodic table, there is a trend of reactivity when we go from top to bottom and from left to right. According to that trend we organize the metals from most active to least active.

Complete step-by-step answer:First, let us talk about their electronic configuration.
Atomic number of $K$(potassium) is$19$. E.C. is$[Ar]4{S^1}$.
Atomic number of $Al$(Aluminium) is$13$. E.C. is$
  [1{s^2}2{s^2}2{p^6}3{s^2}3{p^1}] \\
  [Ne]3{s^2}3{p^1} \\
 $
Atomic number of $Ni$(nickel) is$28$. E.C. is$[Ar]3{d^8}4{s^2}$
Atomic number of $Hg$(mercury) is 80. E.C. is$[Xe]4{f^{14}}5{d^{10}}6{s^2}$
From their electronic configuration we can get an idea of ionization energy. The trend of ionization energy for these metals is:
$K < Al < Ni < Hg$
It means that potassium has minimum ionization energy and mercury have high ionization energy. It means it is easy to remove an electron from the potassium as compared to mercury. We can see their reactivity with cold water, steam, oxygen.

Metals	With cold water	With steam	With oxygen
$K$	It reacts vigorously	it reacts vigorously	it reacts vigorously
$Al$	It does not react	It react moderately	Slow reaction
$Ni$	It does not react	Slow reaction	React when heated
$Hg$	It does not react	It does not react	Reversible reaction

potassium is most reactive. There is an activity series of metals from which can identify which metal is most reactive or which is least reactive. Reactivity series is the series in which metals are arranged according to their reactivity that is from high reactivity to low reactivity. If we see periodic tables the reactivity decreases as we go from left to right across a period. And it increases as we go down a group.
According to reactivity series, the arrangement of the given metals is:
$K > Al > Ni > Hg$ It means that potassium is the most reactive element in the given set of metals and mercury is the least reactive metal.

Note:Try to remember the activity series at least of common metals. Remember that the reactivity series of metals is opposite to the reactivity series of non-metals. Reactivity mainly depends on the ionization energy. If the ionization energy is high of any element then it will be less reactive and if the ionization energy is low of any element then it will be more reactive.