Crookes' spiral periodic system
1888
1888
1915
1940-1950
circa 1930
1801-1892 (prepared); 1946 (element replaced)
1876
1801-1892 (prepared)
1855-1876
1930-1939
1965
1935
1914-1919
1914-1919
1914-1919
1914-1919
1914-1919
1914-1919
1914-1919
1935
1935
1935
1935
1935
1935
1935
1935
1935
1935