List several general properties of the following groups: (a) Alkali metals (b) Noble gases (c) Halogens

Alkali metals are highly reactive elements found in Group 1 of the periodic table, including lithium, sodium, and potassium. They have one electron in their outermost shell, which they readily lose to form positive ions. This reactivity increases down the group, making them react vigorously with water and halogens. They are characterized by low melting and boiling points, and they are typically soft and can be cut with a knife.

Noble gases, located in Group 18 of the periodic table, are known for their lack of reactivity due to having a full valence shell of electrons. This stability makes them inert under most conditions, which is why they are often used in applications requiring non-reactive environments, such as in neon signs or as inert gas shields in welding. The group includes helium, neon, argon, krypton, xenon, and radon, all of which are colorless and odorless at room temperature.

Halogens are found in Group 17 of the periodic table and include fluorine, chlorine, bromine, iodine, and astatine. They are highly reactive nonmetals with seven electrons in their outer shell, which makes them eager to gain an electron to achieve a stable octet configuration. This reactivity decreases down the group, and halogens can form salts when they react with alkali metals. They exist in various states at room temperature: gases (fluorine, chlorine), liquid (bromine), and solid (iodine).