Furthermore, exceptionally in this group, reactivity with boron decreases down the group: lithium reacts completely at 700 °C, but sodium at 900 °C and potassium not until 1200 °C, and the reaction is instantaneous for lithium but takes hours for potassium.
fˌɜːðɚmˈoːɹ, ɛksˈɛpʃənəli ɪn ðɪs ɡɹˈuːp, ɹɪɐktˈɪvᵻɾi wɪð bˈoːɹɑːn dˈiːkɹiːsᵻz dˌaʊn ðə ɡɹˈuːp: lˈɪθiəm ɹɪˈækts kəmplˈiːtli æt sˈɛvənhˈʌndɹɪd dᵻɡɹˈiːz sˈiː, bˌʌt sˈoʊdiəm æt nˈaɪnhˈʌndɹɪd dᵻɡɹˈiːz sˈiː ænd pətˈæsiəm nˌɑːt ʌntˈɪl wˈʌn θˈaʊzənd tˈuːhˈʌndɹɪd dᵻɡɹˈiːz sˈiː, ænd ðə ɹɪˈækʃən ɪz ˌɪnstəntˈeɪniəs fɔːɹ lˈɪθiəm bˌʌt tˈeɪks ˈaʊɚz fɔːɹ pətˈæsiəm.