Question

Which of the following metal does not react with water?
(A) Beryllium
(B) Copper
(C) Iron
(D) Potassium

Answer 1

Hint: The metal belongs to alkaline earth metals. The metal has an electronic configuration $\left[ He \right]2{{s}^{2}}$ and it is a divalent element. Also, the metal has high ionization energy and smaller size compared to other elements in the group.


Complete step by step solution:
  -As we all know, water molecules are composed of one oxygen atom and two hydrogen atoms. Water is naturally found in the solid, liquid and vapor states. And it exhibits polarity. This polarity makes water a good solvent and is generally known as the universal solvent.
  -Due to the abundance of water on earth, it is important to note down that water is involved in many chemical reactions and many of these chemical reactions behave in trends that can be usually categorized using the periodic table.
 - When a metal is allowed to react with water, corresponding metal oxide and hydrogen gas is formed as the products. In the newly formed metal oxides, the metal oxides that are soluble in water dissolve in it to further form metal hydroxide.
 - As we know, all metals do not react with water. The reactivity of metals towards water varies on depending several factors.
 - Alkali metals usually react explosively and violently with water. This is because of the fact that enough heat is given off during the exothermic reaction to ignite the hydrogen gas. The reaction can be written as follows
$2{{M}_{(S)}}+2{{H}_{2}}O\to 2{{M}^{+}}_{(aq)}+2O{{H}_{(aq)}}^{-}+{{H }_{2(g)}}$

    Where M is the metal we are taking to react with water.
 - Among the alkaline earth metals, Beryllium is the only metal that does not react with water. The reason for this being inert with water is due to the high ionization energy and the small size of beryllium compared to other metals.
 - Even if beryllium is heated to red heat it does not react with water or steam. The presence of a resistant outer oxide layer is also a reason for lowering its reactivity at lower temperatures.

Therefore, the answer is option (A). The metal Beryllium does not react with water.


Note: There might be a confusion among options. Potassium being an alkali metal reacts violently with water. In the case of Copper, it does slowly react with water and atmospheric oxygen and a layer of brown-black copper oxide is formed and the metal iron reacts in moist air by oxidation to give a hydrated iron oxide which is also known as rusting.