It's been difficult to explain patterns of toxic mercury in some parts of the world, such as why there's so much of the toxin deposited into ecosystems from the air in the southeastern United States, ...

Sodium and chlorine react vigorously when heated, giving an orange flame and clouds of white sodium chloride.

Chlorine, bromine and iodine are the three common Group 7 elements. Group 7 elements form salts when they react with metals. The term ‘halogen’ means ‘salt former’.

We use aluminum foil every day, but it can be quite reactive under the right circumstances. This gif shows aluminum reacting with bromine, a halogen. Aluminum foil sticks out of the test tube and ...