Final answer:
The elements in Group 17 are known as halogens, which are highly reactive nonmetals with seven valence electrons, existing in various physical states, and are known for forming salts with metals.
Step-by-step explanation:
The elements in Group 17 of the periodic table are commonly known as halogens. These elements share similar chemical properties, which include being highly reactive nonmetals with seven electrons in their outermost energy level. This makes them very electronegative, meaning they have a strong tendency to gain one electron to achieve a full octet in their valence shell, leading to high reactivity, especially with alkali metals and alkaline earth metals. Halogens are found in various physical states across the group: fluorine and chlorine are gases, bromine is a liquid, and iodine is a solid at room temperature.
In summary, the properties that the halogens have in common are that they are all nonmetals, exhibit high reactivity due to their seven valence electrons, and are one electron short of having a full outer energy level, which they fulfill by forming ionic or covalent bonds. Halogens form salts when reacting with metals, which is where the term 'halogen' meaning 'salt-former' comes from.