They all crystallise in the body-centered cubic crystal structure, and have distinctive flame colours because their outer s electron is very easily excited.
ðeɪ ˈɔːl kɹˈɪstɐlˌaɪz ɪnðə bˈɑːdisˈɛntɚd kjˈuːbɪk kɹˈɪstəl stɹˈʌktʃɚ, ænd hæv dɪstˈɪŋktɪv flˈeɪm kˈʌlɚz bɪkˈʌz ðɛɹ ˈaʊɾɚɹ ˈɛs ᵻlˈɛktɹɑːn ɪz vˈɛɹi ˈiːzili ɛksˈaɪɾᵻd.