Colour of these ions may be attributed to
the presence of f electrons Neither La
3+ nor Lu
3+ ion shows any colour
but the rest do so However, absorption bands are narrow, probably
because of the excitation within f level The lanthanoid ions other
than the f 
0 type (La
3+ and Ce
4+) and the f 
14 type (Yb
2+ and Lu
3+) are
all paramagnetic