Atomic size of calcium is _______ than that of potassium.

Answer

To determine the atomic size of calcium in comparison to potassium, we can follow these steps:

1. **Identify the Position of Elements in the Periodic Table**:
- Potassium (K) has an atomic number of 19, and it is located in Group 1 (alkali metals).
- Calcium (Ca) has an atomic number of 20, and it is located in Group 2 (alkaline earth metals).

2. **Understand the Trend of Atomic Size**:
- Atomic size generally increases as you move down a group in the periodic table due to the addition of electron shells.
- Conversely, atomic size decreases as you move from left to right across a period due to the increase in nuclear charge, which pulls the electrons closer to the nucleus.

3. **Compare the Elements**:
- Potassium is to the left of calcium in the periodic table. Since potassium is in Group 1 and calcium is in Group 2, we can analyze their atomic sizes based on their positions.
- As we move from potassium to calcium (left to right), the atomic size decreases because the increased positive charge in the nucleus (more protons) attracts the electrons more strongly, pulling them closer to the nucleus.

4. **Conclusion**:
- Therefore, the atomic size of calcium is **smaller** than that of potassium.

Final Answer: The atomic size of calcium is **smaller** than that of potassium.

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