We present a theoretical study of segregation of sp-elements (Al, Si, P, S,Ga, Ge, As, Se, In, Sn, Sb and Te) at the Sigma5(210) grain boundary (GB) and (210) free surface (FS) in fcc ferromagnetic Ni. Whereas there is a slight enhancement of magnetization at the clean GB and FS with respect to bulk nickel (3–7% and 24%, respectively), the studied impurities entirely kill or strongly reduce ferromagnetism at the GB/FS and in its vicinity so that magnetically dead layers are formed. This effect is due to the hybridization of the impurity sp-states and Ni d-states. We determine the preferred segregation sites at the Sigma5(210) GB for the sp-impurities, their segregation enthalpies and strengthening/embrittling energies with their chemical and mechanical components. We find interstitially segregated Si and P and substitutionally segregated Al as a GB cohesion enhancer and interstitially segregated S, Ge, As, Se and substitutionally segregated Ga, In, Sn, Sb and Te as GB embrittlers in Ni.