Alkali Metals and Halogens

Physical properties of Alkali Metals

Alkali metals are characterised by being extremely soft (cuttable with knife), having low densities and low melting/boiling points, best conductors of heat and electricity

Chemical properties of Alkali Metals

Every element in the group has one electron in outer s-orbital, elements react vigorously with water to produce a strong alkali solution, tarnishes instantly in air forming oxides, react violently with halogens to form white, ionic crystalline halides, soluble in liquid ammonia

How reactive is Alkali Metals and how does reactivity change down the group?

Alkali metals are among the most reactive metals, they tarnish quickly in air forming oxides and they all react with water to form, metal hydroxide and hydrogen gas. Reactivity increases down the group.

Why do Alkali Metals show those reactivity patterns?

Alkali metals show high to low reactivity down the group because they have only one electron in their outermost shell which they must lose to achieve a stable, full shell electron configuration

Physical properties of Halogens

Low melting/boiling points due to weak intermolecular forces, poor conductors of heat and electricity, highly coloured, when solid they are dull and brittle, generally soluble decreasing down the group, densities increase down the group

Chemical properties of halogens

Highly reactive non metals (decreasing down the group), they all produce metals halides (salts) with alkali metals, they also react with each other in displacement reactions

How reactive are Halogens and how does reactivity change within the group?

Reactivity decrease down the group as atoms increase in size, reducing their ability to attract an electron to complete their outer shell

Why do halogens show these reactivity patterns?

High reactivity moves down the group due to their atomic structure, electronic configuration and changes in electro-negativity

Elements in Alkali metals

Lithium, Sodium, Potassium, Rubidium, Cesium, Francium

Elements in Halogens

Flourine, Chlorine, Bromine, Iodine, Astatine, Tennessine

What are Isotopes?

Stokes of the same element all have the same number of protons but the number of neutrons in the nuclei can be different

How do you find the mass number?

The mass number of an atom is found by adding the number of protons and neutrons. Different isotopes are written with their atomic mass numbers after the element name