Question

The most electropositive element is
(A) Na
(B) Al
(C) F
(D) K

Answer 1

Hint: The periodic table is made in such a form that it can show the variations of several properties of the atoms both along the period and down the group. This is the reason why it is arranged based on the atomic number and not atomic mass. Electropositivity depends on the ability to lose an electron. Among the given elements, the most electropositive element will be on the right side of the period as well as downward in the group. This is the trend of electropositivity in the periodic table.

Complete step by step solution:
-There are 7 periods and 18 groups in periodic tables where atoms are arranged on the increasing order of their atomic number because the atomic number gives us the number of electrons of the atom. Electrons only decide the chemical properties of an atom as they are loosely held by the atom.
-Electropositivity is the opposite of electronegativity. It is the tendency of an atom to lose the electrons and achieve the octet configuration of the nearest noble gas. As it involves the losing of electrons, it is completely opposite to electronegativity.
-Along the period, electronegativity increases. So electropositivity decreases.
Down the group, electronegativity decreases and so the electropositivity increases.
-Thus according to this order, we see that the group 1 elements are the most electropositive and among them, the strength increases down the group.They easily lose 1 electron to form cation. So they are called metals and thus have maximum metallic character.
-Now looking at the options, we see that only 2 elements from the given options belong to group 1 elements. They are Na and K. We have already discussed the trend in the electropositive nature of the elements down the group. So, from the given options, K is the most electropositive element.

Therefore the correct option for the question is D. Potassium.


Note: The bottommost atom of the group 1 elements is Francium and not Cesium. But the most electropositive element of the periodic table is Cesium and not Francium. The reason for this is that Francium is a radioactive element and so it is not stable. So, although Fr is theoretically the most electropositive element of the periodic table, yet Cs is practically the most electropositive element. Its electronic configuration is $\left[Xe\right]6s^1$
$$Cs\to C{s}^{1+}+1e^{-}$$