- Fluorine (F) has as gases. Pale yellow and harmful organisms. By pure fluorine is highly dangerous as it can cause burns on the skin. Typically utilized in a fluorine compound such as sodium chloride fluoride (NaF), which, if used in small amounts added to toothpaste to help prevent tooth decay.
- Chlorine (Cl) exist as gases. Ekiim yellowish color. Heavier than air. Severely infested. And serious toxicity. Has the ability to kill bacteria as well. Is used to fill the water or in the pool. To clean water. Chlorine is found in the form of sea salt and other compounds, such as sodium chloride (NaCl) or sodium chloride, etc.
- Bromine (Br) is the only element in Group 7A elements pigs marked with red liquid can evaporate easily at room temperature. Harmful to human tissue. The vapors can cause irritation to eyes and skin sensitive.
- Iodine (I) is listed as insoluble solids is essential to the survival of the organism. Because the element is an element which is an essential element in the production of some important hormones. It is also useful in the production of iodine disinfectant and dye.