Lithium, sodium, and potassium were part of the discovery of periodicity, as they are among a series of triads of elements in the same group that were noted by Johann Wolfgang Döbereiner in 1850 as having similar properties.
lˈɪθiəm, sˈoʊdiəm, ænd pətˈæsiəm wɜː pˈɑːɹt ʌvðə dɪskˈʌvɚɹi ʌv pˌiəɹɪˌɑːdˈɪsᵻɾi, æz ðeɪ ɑːɹ ɐmˌʌŋ ɐ sˈɪɹiz ʌv tɹˈaɪædz ʌv ˈɛlɪmənts ɪnðə sˈeɪm ɡɹˈuːp ðæt wɜː nˈoʊɾᵻd baɪ jˈoʊhɑːn wˈʊlfɡæŋ dˈɜːbɚɹˌiːnɚɹ ɪn wˈʌn θˈaʊzənd ˈeɪthˈʌndɹɪd fˈɪfti æz hˌævɪŋ sˈɪmɪlɚ pɹˈɑːpɚɾiz.