Respuesta :
Likely there is a typo in the second option. If the correct year is 1890, that is the right answer.
JJ Thompson in the 1890 decade discovered that the particles that consituted the cathodic rays had a mass much, much smaller than the ligthest atom (the hydrogen), identifying the electron as a particle of the atom.
Regarding the other options:
a) Thompson model was not that the electrons orbited but that the atoms were a solid sphere with the electrons embedded.
c) John Dalton lived was born in 1776
d) Niels Bohr model was that negatively charged particles orbitted a positively charged nucleus.
JJ Thompson in the 1890 decade discovered that the particles that consituted the cathodic rays had a mass much, much smaller than the ligthest atom (the hydrogen), identifying the electron as a particle of the atom.
Regarding the other options:
a) Thompson model was not that the electrons orbited but that the atoms were a solid sphere with the electrons embedded.
c) John Dalton lived was born in 1776
d) Niels Bohr model was that negatively charged particles orbitted a positively charged nucleus.
I took the test and the correct answer B or the second option: about 1990, jj. thompson discovered electrons were negatively charged particles.