Before the 20 th century, relatively little was known about the atom. The concept that objects were made of smaller particles that could not become any smaller was theorised by two Greek philosophers; Leucippus and Democritus. They believed that if you keep cutting an object consistently, there will come a point where it will not be able to be cut any further. Therefore, the theory of the atom was established but it was not possible to explore it further. In 1897, JJ Thompson discovered the electron. He subjected a hot metal coil into an electric field, thereby producing the first cathode ray. Importantly, he noticed that the cathode ray could be deflected by a magnetic field, when viewed under a cloud chamber, and realised that it was negatively charged. As the atom is neutral, he proposed that there must be positively charged particles that give the atom an overall neutrality. JJ Thompson put forward the plumpudding model theory of the atom; that positively charged particles and negatively charged particles are mixed together in an infinitely small region of space. In 1911, Ernest Rutherford carried out the gold leaf experiment. He fired alpha particles at a gold leaf and found that although most of the alpha particles went through, some were deflected. Occasionally, he also saw a small spark upon collision. From this, he theorised that the atom cannot be a mixture of negatively and positively charged particles, but rather has a dense core of positively charged particles. He called these particles protons. He also realised that most of the atom is empty space. In 1932, James Chadwick performed an experiment that discovered the final component of the atom. On observation of alpha decay, he noticed that one of the particles being emitted was not deflected by a magnetic field, hence being neutrally charged. He called this particle the neutron. Thus, the Rutherford Model of the Atom was born; the protons and neutrons form the nucleus of the atom, which electrons in spinning in orbit.
Question: The direction of particle deflection was determined using the cloud chamber.
Options:
A. true, B. false, C. uncertain
Answer: A