Why do some atoms combine while others do not?

Why do atoms combine?

Why do some materials burn and some do not?

Why do atoms combine and form molecules?

Place a fist full of Bengal gram (or any other seeds) seeds in a bowl of water. Do you find some seeds float while others sink? Which seeds do you think will not germinate and why?

Why do some metals replace the other metals from solution ?

Place a fist full of Bengal gram (or any other seeds) seeds in a bowl of water. Do you find some seeds float while others sink? Which seeds do you think farmers should use for sowing in the field.

Why do seeds float on water?