Calcium is an element with atomic number 20. Stating reason answer each of the following questions: (i) Is calcium a metal or non-metal? (ii) Will its atomic radius be larger or smaller than that of potassium with atomic number 19? (iii) Write the formula of its oxide.

Explanation

### Step-by-Step Solution:

**(i) Is calcium a metal or non-metal?**

To determine whether calcium is a metal or a non-metal, we need to look at its electronic configuration. The atomic number of calcium is 20, which means it has 20 electrons. The electronic configuration of calcium is 2, 8, 8, 2.

Metals are characterized by their ability to lose electrons easily and form positive ions (cations). Calcium has two electrons in its outermost shell (the fourth shell), which it can easily lose to achieve a stable electronic configuration similar to that of the nearest noble gas, argon. When calcium loses these two electrons, it forms a Ca²⁺ ion.

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