Slavs
Slavs are the largest ethno-linguistic group in Europe. Present-day Slavic people are classified into East Slavs (chiefly Belarusians, Russians, Rusyns, and Ukrainians), West Slavs (chiefly Czechs, Kashubs, Moravians, Poles, Silesians, Slovaks and Sorbs), and South Slavs (chiefly Bosniaks, Bulgarians, Croats, Macedonians, Gorani, Pomaks, Montenegrins, Serbs and Slovenes).
Name of Ukraine
The preposition "na" continues to be used with Ukraine (and with Rus') in other West Slavic (Polish, Czech, Slovak).
While South Slavic (Serbo-Croatian, Slovene) uses "v" exclusively.