Chlorine, bromine and iodine resemble one another since they __

Explanation

Chlorine, bromine, and iodine are all part of Group 17 in the periodic table, also known as halogens. They share similar chemical properties due to their similar electronic configurations. All halogens have seven electrons in their outermost shell, which gives them a strong tendency to gain one electron to achieve a stable noble gas configuration.

The correct answer isOption A: dissolve in alkalis. Halogens react with alkalis to form salts and water. For example, when chlorine reacts with sodium hydroxide (an alkali), it forms sodium chloride (a salt) and water:

\[{ Cl2 + 2NaOH -> 2NaCl + H2O }\]

This property is common among halogens due to their reactivity and electronegativity. The other options do not correctly describe the similarities among chlorine, bromine, and iodine:

Option B: Not all halogens react violently with hydrogen without heating. Chlorine reacts with hydrogen at room temperature, while bromine and iodine require heating for the reaction to occur.

Option C: They do not displace each other from solutions of their salts. The ability to displace other halogens depends on their reactivity, which decreases down the group. For example, chlorine can displace bromine and iodine, but iodine cannot displace chlorine or bromine.

Option D: They are not all gases. Chlorine is a gas, bromine is a liquid, and iodine is a solid at room temperature.

Option E: They are not all liquids. As mentioned earlier, their physical states differ at room temperature.

In summary, chlorine, bromine, and iodine resemble one another because they all dissolve in alkalis, which is a characteristic property of halogens due to their electronic configurations and reactivity.