Question

1. oxygen (o), sulfur (s), and selenium (se) are nonmetals. which one is the most reactive, and why? which group do they belong to? are they in the same period?

Explanation:

Step1: Identify group in periodic table

Oxygen (O), Sulfur (S), and Selenium (Se) belong to Group 16 (also called the chalcogens) in the periodic table. This is because they all have 6 valence - electrons.

Step2: Analyze periods

Oxygen is in Period 2, Sulfur is in Period 3, and Selenium is in Period 4. So they are not in the same period.

Step3: Determine reactivity

The reactivity of non - metals in Group 16 decreases down the group. Oxygen is the most reactive among them because as we move down the group, the atomic size increases, and the attraction between the nucleus and the incoming electron decreases.

Answer:

Oxygen (O), Sulfur (S), and Selenium (Se) belong to Group 16. They are not in the same period. Oxygen is the most reactive.