Question

fritz strassmann
infrared radiation
radio waves
otto hahn
x - rays
lise meitner
ultraviolet radiation
polonium
marie sklodowska curie
enrico fermi
antoine - henri becquerel
thorium
gamma rays
radium
uranium
blank first discovered radioactivity in 1896 by placing radioactive blank minerals on photographic plates in an attempt to look for blank

Explanation:

1. The first blank: Antoine - Henri Becquerel is the scientist who first discovered radioactivity in 1896.
2. The second blank: He used uranium minerals (uranium is a radioactive element, and he was working with uranium salts).
3. The third blank: His attempt was to look for X - rays (he was investigating if uranium salts could produce X - rays when exposed to sunlight, but later found radioactivity).

Answer:

First blank: Antoine - Henri Becquerel; Second blank: uranium; Third blank: X - rays