Why is potassium more metallic than sodium. Give reason for the choice.

Options

A. Both have 1 electron in their outermost shell.
B. Both are highly electropositive.
C. Sodium is larger in size than potassium.
D. Potassium is larger in size than sodium.

Answer

To understand why potassium (K) is more metallic than sodium (Na), we need to analyze the properties of these two alkali metals in terms of their atomic structure and behavior.

### Step-by-Step Solution:

1. **Identify the Group**: Both sodium and potassium belong to Group 1 of the periodic table, known as the alkali metals. They have similar properties but differ in their atomic size.

2. **Atomic Size**: Sodium has an atomic number of 11, while potassium has an atomic number of 19. As we move down the group in the periodic table, the atomic size increases due to the addition of electron shells. Potassium has one more electron shell than sodium.

3. **Distance from Nucleus**: In sodium, the outermost electron is located in the third shell (3s), while in potassium, the outermost electron is in the fourth shell (4s). The increased distance of the outermost electron from the nucleus in potassium results in a weaker electrostatic attraction between the positively charged nucleus and the negatively charged outer electron.

4. **Nuclear Attraction Force**: The nuclear attraction force is stronger in sodium because its outer electron is closer to the nucleus. This means that sodium holds onto its outer electron more tightly compared to potassium.

5. **Tendency to Lose Electrons**: Metals are characterized by their ability to lose electrons easily. Since potassium's outer electron is further away from the nucleus and experiences less nuclear attraction, it can lose this electron more readily than sodium can. This makes potassium more metallic in character.

6. **Electropositivity**: Electropositivity refers to the ability of an element to donate electrons. Since potassium can lose its outer electron more easily than sodium, it is considered to be more electropositive and hence more metallic.

### Conclusion:
Potassium is more metallic than sodium because it has a larger atomic size, which results in a weaker nuclear attraction force acting on its outermost electron. This allows potassium to lose its outer electron more easily, making it a better metal.