According to Slater's rule, correct order of Zeff. on valence shell electron is : — Periodic Table and Periodicity Chemistry Question

💡 Solution & Explanation

Step 1: Recall that electropositive (metallic) character increases down a group and decreases across a period. Step 2: Group 1 alkali metals are the most electropositive elements. Among the choices, Rubidium (Rb) is an alkali metal located in the 5th period. Step 3: Thus, Rubidium is the most electropositive element, corresponding to option (b).