Question

Sodium atom and sodium ion:
(A) Are chemically the same
(B) Have the same number of protons
(C) Have the same number of electrons
(D) React spontaneously with water

Answer 1

Hint: Firstly to start with the answer we need to understand the difference between atom and ions. Ions are charged species while atoms are an uncharged species. Let us study that separately. Sodium ion and atom will have differences in their properties for sodium atom and sodium Ion, let us briefly describe them one by one now.

Step by step answer:
Firstly you need to understand the position of sodium in the periodic table. The sodium element lies in the first group of periodic tables called alkali metals.
To start with, let us study the properties of sodium atoms. It has an atomic mass of 23 and atomic number of 11.
We know, atomic number is equal to the number of protons, thus the number of protons in a sodium atom is 11. Sodium atoms are electrically neutral so the number of protons is equal to the number of electrons and thus, we can say that there are 11 electrons as well in sodium atoms.
Now let us discuss sodium ion, in sodium ion the atomic number of sodium is 11 and we know that there is no difference in the number of protons even when ion is formed. Now since we know sodium is a metal so it will form a cation by losing one electron as it is a monovalent atom. Total electrons in sodium atoms are 11 electrons as the ion is formed when an electron is lost. Thus, the total number of electrons in sodium ions becomes 10.
Now we also know that the chemical properties are depending on the number of electrons so option (A) is incorrect as chemical properties are different, while option (C) is also incorrect as number of electrons are different.
Now, reaction of sodium atom and reaction of sodium ion with water has to be discussed, we know that sodium atom reacts vigorously while Sodium ion does not react at all with water. Thus option (D) is also incorrect.
In any charged ion or an atom, there is no change in the number of protons, as protons remain the same in sodium atoms and sodium ions, as they lie inside the nucleus.

Hence, the correct option is (B) have the same number of protons.

Note: Remember the atom and ion are different. They differ in their chemical properties due to the difference in number of electrons. But protons are never changed as they exist inside the nucleus. Reaction with water is different for atoms and ions, as all chemical properties or reactions with water, any such property is due to the number of valence electrons. And if the ion has completed octet, then it does not react with water at all.