Rubidium and caesium were the first elements to be discovered using the spectroscope, invented in 1859 by Robert Bunsen and Gustav Kirchhoff.
ɹuːbˈɪdiəm ænd sˈiːsiəm wɜː ðə fˈɜːst ˈɛlɪmənts təbi dɪskˈʌvɚd jˈuːzɪŋ ðə spˈɛktɹəskˌoʊp, ɪnvˈɛntᵻd ɪn wˈʌn θˈaʊzənd ˈeɪthˈʌndɹɪd fˈɪfti nˈaɪn baɪ ɹˈɑːbɚt bˈʌnsən ænd ɡˈʌstæv kˈɜːtʃhɔf.