The model of the atom has changed over time in light of new knowledge and discoveries. which option correctly describes one such change? a. about 1915, jj. thompson developed an atomic model where negatively charged particles orbit a positively charged nucleus. b. about 1990, jj. thompson discovered electrons were negatively charged particles. c. in 420 b. c., john dalton developed the idea that small atoms combined to form molecules. d. about 1900, neils bohr developed an atomic model where positively charged particles orbit a negatively charged nucleus.

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.

Kinetic energy = 1/2mv^2. since the mass is constant we can form a ratio of it's kinetic energy at 60 divided by that at 30 to see ke(60)/ke(30) = +(60^2)/30^2). this may be said to 300% increase.