Group I alkali metals and Group VII halogens

Learning objectives

Describe the Group I alkali metals lithium, sodium and potassium as relatively soft metals whose melting points decrease and whose density and reactivity with water increase down the group

Describe the reactions of the alkali metals with water to form a metal hydroxide and hydrogen, and predict the properties of other Group I elements from the trends

Describe the Group VII halogens chlorine, bromine and iodine as diatomic non-metals whose density increases and reactivity decreases down the group, and state their appearance at room temperature: chlorine a pale yellow-green gas, bromine a red-brown liquid and iodine a grey-black solid

Predict the properties of other Group VII elements, such as fluorine and astatine, from the trends in the group

Describe and explain the displacement reactions of halogens with other halide ions, e.g. chlorine displacing bromide or iodide ions from aqueous solution, in terms of the trend in reactivity