Final answer:
Fluorine compounds in toothpaste and water are used to prevent tooth decay.
Step-by-step explanation:
The subject of this question is Chemistry.
A highly reactive, gaseous, non-metal referred to in the question is fluorine. Its compounds are added to some toothpaste and many urban water supplies to prevent tooth decay.
Fluoride ions help protect our teeth by reacting with hydroxylapatite in tooth enamel to form fluorapatite, which is more resistant to acid attacks. Fluoride is commonly added to drinking water, toothpastes, and mouthwashes to promote oral health.