All the alkali metals have odd atomic numbers; hence, their isotopes must be either odd–odd (both proton and neutron number are odd) or odd–even (proton number is odd, but neutron number is even).
ˈɔːl ðɪ ˈælkəlˌaɪ mˈɛɾəlz hæv ˈɑːd ɐtˈɑːmɪk nˈʌmbɚz; hˈɛns, ðɛɹ ˈaɪsətˌoʊps mˈʌst biː ˈiːðɚɹ ˈɑːd ˈɑːd bˈoʊθ pɹˈoʊtɑːn ænd nˈuːtɹɑːn nˈʌmbɚɹ ɑːɹ ˈɑːd ɔːɹ ˈɑːd ˈiːvən pɹˈoʊtɑːn nˈʌmbɚɹ ɪz ˈɑːd, bˌʌt nˈuːtɹɑːn nˈʌmbɚɹ ɪz ˈiːvən.