They can all be cut easily with a knife due to their softness, exposing a shiny surface that tarnishes rapidly in air due to oxidation by atmospheric moisture and oxygen (and in the case of lithium, nitrogen).
ðeɪ kæn ˈɔːl biː kˈʌt ˈiːzili wɪð ɐ nˈaɪf dˈuː tə ðɛɹ sˈɔftnəs, ɛkspˈoʊzɪŋ ɐ ʃˈaɪni sˈɜːfɪs ðæt tˈɑːɹnɪʃᵻz ɹˈæpɪdli ɪn ˈɛɹ dˈuː tʊ ˌɑːksɪdˈeɪʃən baɪ ˌætməsfˈɛɹɪk mˈɔɪstʃɚ ænd ˈɑːksɪdʒən ænd ɪnðə kˈeɪs ʌv lˈɪθiəm, nˈaɪtɹədʒən.