Question

Sodium has __________ as compared to potassium.
(A) less electronegativity
(B) more ionization potential
(C) large atomic radius
(D) lower melting point

Answer 1

Both Sodium and potassium belong to the first group of the periodic table (Alkali Metal). Both are classified as s-block elements since valence electrons enter into the s-subshell. These show similarity in several of their physical and chemical properties since they belong to the same group of the periodic table however they also show some differences.

Complete answer:
The main reason for the point of difference is due to the difference in the size of atoms. Sodium is smaller in size than that of Potassium that lies below it. Sodium has an Electronic configuration of $\left[ {Ne} \right]3{s^1}$ while Potassium has an Electronic configuration of $\left[ {Ar} \right]4{s^1}$. Sodium $\left( {Na} \right)$ has an atomic number of 11 and Potassium $\left( K \right)$ has an atomic number 19.
Now we look at the options one by one-
(A)Electronegativity is the tendency of an atom to attract the shared pair of electrons towards itself. As we move from left to right in a period it increases and from top to bottom it increases. So the value of Electronegativity is greater for Sodium than Potassium. Hence the option is incorrect.
(B) Ionization Potential is the amount of energy required to remove an electron from the atom. Sodium contains 3s electrons while Potassium contains 4s electrons hence Sodium is closer to Nucleus. So it requires more energy to remove the electron from sodium as compared to Potassium. Hence option is correct.
(C) Sodium is smaller in size than Potassium so the option is incorrect.
(D) Sodium has Melting point greater than that of Potassium due to greater Metallic bonding. Hence option is incorrect.
Hence Option (B) is correct.

Note:
Both Sodium and Potassium are highly reactive. These react with both air and water hence they are stored in kerosene. Sodium and Potassium are very important for the functioning of the human body. Sodium maintains fluid levels outside the cell while Potassium maintains fluid levels inside the cell.