In the alkali metals, the outermost electron only feels a net charge of +1, as some of the nuclear charge (which is equal to the atomic number) is cancelled by the inner electrons; the number of inner electrons of an alkali metal is always one less than the nuclear charge.
ɪnðɪ ˈælkəlˌaɪ mˈɛɾəlz, ðɪ ˈaʊɾɚmˌoʊst ᵻlˈɛktɹɑːn ˈoʊnli fˈiːlz ɐ nˈɛt tʃˈɑːɹdʒ ʌv plˈʌs wˈʌn, æz sˌʌm ʌvðə nˈuːklɪɹ tʃˈɑːɹdʒ wˌɪtʃ ɪz ˈiːkwəl tə ðɪ ɐtˈɑːmɪk nˈʌmbɚ ɪz kˈænsəld baɪ ðɪ ˈɪnɚɹ ᵻlˈɛktɹɑːnz; ðə nˈʌmbɚɹ ʌv ˈɪnɚɹ ᵻlˈɛktɹɑːnz əvən ˈælkəlˌaɪ mˈɛɾəl ɪz ˈɔːlweɪz wˈʌn lˈɛs ðɐn ðə nˈuːklɪɹ tʃˈɑːɹdʒ.