The second ionisation energy of all of the alkali metals is very high as it is in a full shell that is also closer to the nucleus; thus, they almost always lose a single electron, forming cations.
ðə sˈɛkənd ˌaɪənəzˈeɪʃən ˈɛnɚdʒi ʌv ˈɔːl ʌvðɪ ˈælkəlˌaɪ mˈɛɾəlz ɪz vˈɛɹi hˈaɪ ˌæzɪtˌɪz ɪn ɐ fˈʊl ʃˈɛl ðæt ɪz ˈɔːlsoʊ klˈoʊsɚ tə ðə nˈuːklɪəs; ðˈʌs, ðeɪ ˈɔːlmoʊst ˈɔːlweɪz lˈuːz ɐ sˈɪŋɡəl ᵻlˈɛktɹɑːn, fˈɔːɹmɪŋ kˈæɾaɪənz.