What is the number of elements in:
1. `1^(st)` period and
2. `2^(nd)` period of modern periodic table.

Explanation

To determine the number of elements in the first and second periods of the modern periodic table, we can follow these steps:

### Step 1: Identify the First Period
- The first period of the periodic table consists of the first two elements.
- These elements are Hydrogen (H) and Helium (He).

### Step 2: Count the Elements in the First Period
- Since there are only two elements (H and He) in the first period, we conclude that:
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