The essentials: alkali metals: lithium, sodium, potassium, rubidium, caesium and francium; they are all metals and form simple ionic compounds which are soluble in water. The trends in the properties of the group 1 metals and their compounds can be explained in terms of variations in their atomic radii and ionization energies. packed. Ionic and metallic radius increases down the group. Csbr and csi have the (8,8)-coordinate caesium-chloride structure. The chemical properties of li are anomalous due to its small ionic radius and tendency to exhibit covalent bonding. o. Lithium can exhibit a high degree of covalent character in its bonding; this covalent character is due to the high polarizing power of the li+ ion associated with high charge density. o. Lithium forms the normal oxide when burnt in oxygen whereas other. Group 1 elements form peroxides or superoxides. o. Lithium nitrate decomposes directly to the oxide whereas the other alkali metals initially form nitrites, mno2.