Odd–odd primordial nuclides are rare because most odd–odd nuclei are highly unstable with respect to beta decay, because the decay products are even–even, and are therefore more strongly bound, due to nuclear pairing effects.
ˈɑːd ˈɑːd pɹɪmˈoːɹdɪəl nˈuːklaɪdz ɑːɹ ɹˈɛɹ bɪkˈʌz mˈoʊst ˈɑːd ˈɑːd nˈuːklɪi ɑːɹ hˈaɪli ʌnstˈeɪbəl wɪð ɹᵻspˈɛkt tə bˈeɪɾə dᵻkˈeɪ, bɪkˈʌz ðə dᵻkˈeɪ pɹˈɑːdʌkts ɑːɹ ˈiːvən ˈiːvən, ænd ɑːɹ ðˈɛɹfoːɹ mˈoːɹ stɹˈɔŋli bˈaʊnd, dˈuː tə nˈuːklɪɹ pˈɛɹɪŋ ɪfˈɛkts.