The prefix eka- comes from the Sanskrit word for “one.” Mendeleev used this prefix to indicate that the unknown element was one place away from the known element that followed the prefix. For example, eka-silicon, which we now call germanium, is one element below silicon. Mendeleev also predicted the existence of eka-manganese, which was not experimentally confirmed until 1937 because this element is radioactive and does not occur in nature. Based on the periodic table shown in Figure 7.1, what do we now call the element Mendeleev called eka-manganese?

Figure 7.1

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H Не BCNOF Al Si PS C Ar K Ca Sc Ti v Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr Li Be Ne Na Mg Са V Rb Sr Y Zr Nb Mo Te Ru Rh Pd Ag Cd In Sn Sb Te I Xe Cs Ba Lu Hf Ta w Re Os Ir Pt Au Hg TI Pb Bi Po At Rn Rb Sr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd Хе Fr Ra Lr Rf Db Sg Bh Hs Mt Ds Rg Cn La Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Ac Th Pa U Np Pu Am Cm Bk Cf Es Fm Md No Ancient Times Middle Ages-1700 1735–1843 1843-1886 1894–1918 1923–1961 (9 elements) (6 elements) (42 elements) (18 elements) (11 elements) (17 elements) 1965- (9 elements)