Why do elements in the same group have similar physical and chemical properties?

🔷 Explanation:

1. 🔹 Same Valence Electron Configuration

   • For example, all elements in Group 1 have the configuration ns¹, meaning they have 1 electron in their outer shell.

   • Similarly, Group 17 elements have ns² np⁵ (7 valence electrons).

2. 🔹 Valence Electrons Determine Reactivity

   • Chemical reactions occur mainly due to the gain, loss, or sharing of valence electrons.

   • Since group members have the same number of valence electrons, their chemical behavior (like reactivity, type of bonds, etc.) remains similar.

3. 🔹 Trends in Physical Properties

   • Properties like melting point, boiling point, atomic size, and density show a gradual change down the group but follow a similar trend.

   • Example: Group 18 (noble gases) are all inert, monoatomic gases, even though their boiling points vary.

✅ Conclusion:

Elements in the same group behave similarly because they have the same number of valence electrons, which governs their chemical reactions and many physical properties.

(9)