Answer:
Pair 1 : Na & Rb
Pair 2 : O & Se
Pair 3 : Ne & Kr
Explanation:
Pair 1 are Group 1 elements in the periodic table. They are electro-positive elements that exhibit metallic properties.
Pair 2 are Group 6 elements in the periodic table. They are electro-negative elements that exhibit non-metallic properties.
Pair 3 are Group 8 or Group 0 elements in the periodic table. They are mainly inert gases.