Which one of the following statements is correct ?

CONCEPT:

Basic Atomic Structure and Properties

• Atoms are the basic building blocks of matter, consisting of subatomic particles: protons, neutrons, and electrons.
• Protons are positively charged, electrons are negatively charged, and neutrons are neutral.
• The mass of an electron is significantly smaller compared to a proton or neutron.
• Isotopes are variants of an element with the same number of protons but a different number of neutrons.

EXPLANATION:

• "A neutron is formed by combination of an electron and a proton. Therefore, it is neutral."
  • This statement is incorrect. Neutrons are fundamental particles and are not formed by the combination of a proton and an electron.
• "The mass of an electron is about 1/2000 times that of a proton."
  • This statement is correct. The mass of an electron is approximately 1/1836 times the mass of a proton, which is close to 1/2000.
•  "An isotope of cobalt is used in the treatment of goiter."
  • This statement is incorrect. The isotope of iodine, not cobalt, is used in the treatment of goiter.
• "J. J. Thomson proposed that the nucleus of an atom contains only neutrons."
  • This statement is incorrect. J. J. Thomson proposed the "plum pudding model," and the discovery of the neutron came later by James Chadwick.

Therefore, the correct statement is that the mass of an electron is about 1/2000 times that of a proton.