In aqueous solution, the alkali metal ions exist as octahedral hexahydrate complexes ([M(H2O)6)]+), with the exception of the lithium ion, which due to its small size forms tetrahedral tetrahydrate complexes ([Li(H2O)4)]+); the alkali metals form these complexes because their ions are attracted by electrostatic forces of attraction to the polar water molecules.
ɪn ˈeɪkwɪəs səlˈuːʃən, ðɪ ˈælkəlˌaɪ mˈɛɾəl ˈaɪɑːnz ɛɡzˈɪst æz ˌɑːktɐhˈiːdɹəl hˈɛksɐhˌaɪdɹeɪt kˈɑːmplɛksᵻz ˈɛm ˈeɪtʃ tˈuː ˈoʊ sˈɪks plˈʌs, wɪððɪ ɛksˈɛpʃən ʌvðə lˈɪθiəm ˈaɪɑːn, wˌɪtʃ dˈuː tʊ ɪts smˈɔːl sˈaɪz fˈɔːɹmz tˌɛtɹɐhˈiːdɹəl tˈɛtɹɐhˌaɪdɹeɪt kˈɑːmplɛksᵻz lˈaɪ ˈeɪtʃ tˈuː ˈoʊ fˈoːɹ plˈʌs; ðɪ ˈælkəlˌaɪ mˈɛɾəlz fˈɔːɹm ðiːz kˈɑːmplɛksᵻz bɪkˈʌz ðɛɹ ˈaɪɑːnz ɑːɹ ɐtɹˈæktᵻd baɪ ɪlˌɛktɹoʊstˈæɾɪk fˈoːɹsᵻz ʌv ɐtɹˈækʃən tə ðə pˈoʊlɚ wˈɔːɾɚ mˈɑːlɪkjˌuːlz.