A helium nucleus was presumed to be composed of four protons plus two "nuclear electrons" (electrons bound inside the nucleus) to cancel two of the charges.
ɐ hˈiːliəm nˈuːklɪəs wʌz pɹɪzˈuːmd təbi kəmpˈoʊzd ʌv fˈoːɹ pɹˈoʊtɑːnz plˈʌs tˈuː "nˈuːklɪɹ ᵻlˈɛktɹɑːnz" ᵻlˈɛktɹɑːnz bˈaʊnd ɪnsˈaɪd ðə nˈuːklɪəs tə kˈænsəl tˈuː ʌvðə tʃˈɑːɹdʒᵻz.